If you are using the default values of the In Size the project will run fine, but changing the values will make the engine crash.
This was reported and tested in 4.25 (CL-13144385) and reproduced in Main 4.26 (CL-13230104)
Results: The Engine will crash with an Assertion
Expected: Create a Widget in memory without the engine crashing
[2020.05.08-16.56.04:775][310]LogWindows: Error: === Critical error: === [2020.05.08-16.56.04:775][310]LogWindows: Error: [2020.05.08-16.56.04:775][310]LogWindows: Error: Assertion failed: ContainerPtr [File:D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\CoreUObject\Public\UObject/UnrealType.h] [Line: 356] [2020.05.08-16.56.04:775][310]LogWindows: Error: [2020.05.08-16.56.04:775][310]LogWindows: Error: [2020.05.08-16.56.04:775][310]LogWindows: Error: [2020.05.08-16.56.04:775][310]LogWindows: Error: [Callstack] 0x00007ffa793aa799 KERNELBASE.dll!UnknownFunction [] [2020.05.08-16.56.04:775][310]LogWindows: Error: [Callstack] 0x00007ffa04fe0b06 UE4Editor-Core.dll!ReportAssert() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Core\Private\Windows\WindowsPlatformCrashContext.cpp:1451] [2020.05.08-16.56.04:775][310]LogWindows: Error: [Callstack] 0x00007ffa04fe3ee8 UE4Editor-Core.dll!FWindowsErrorOutputDevice::Serialize() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Core\Private\Windows\WindowsErrorOutputDevice.cpp:78] [2020.05.08-16.56.04:775][310]LogWindows: Error: [Callstack] 0x00007ffa04d70c0d UE4Editor-Core.dll!FOutputDevice::LogfImpl() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Core\Private\Misc\OutputDevice.cpp:61] [2020.05.08-16.56.04:775][310]LogWindows: Error: [Callstack] 0x00007ffa04cfbe95 UE4Editor-Core.dll!AssertFailedImplV() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Core\Private\Misc\AssertionMacros.cpp:100] [2020.05.08-16.56.04:775][310]LogWindows: Error: [Callstack] 0x00007ffa04cfe1d0 UE4Editor-Core.dll!FDebug::CheckVerifyFailedImpl() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Core\Private\Misc\AssertionMacros.cpp:450] [2020.05.08-16.56.04:775][310]LogWindows: Error: [Callstack] 0x00007ffa460eedd2 UE4Editor-CoreUObject.dll!UObject::execStructConst() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\ScriptCore.cpp:3288] [2020.05.08-16.56.04:775][310]LogWindows: Error: [Callstack] 0x00007ffa01e9abb1 UE4Editor-Engine.dll!UKismetSystemLibrary::execSetStructurePropertyByName() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Engine\Classes\Kismet\KismetSystemLibrary.h:843] [2020.05.08-16.56.04:775][310]LogWindows: Error: [Callstack] 0x00007ffa45e50ab4 UE4Editor-CoreUObject.dll!UFunction::Invoke() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\Class.cpp:5542] [2020.05.08-16.56.04:775][310]LogWindows: Error: [Callstack] 0x00007ffa4609ff9d UE4Editor-CoreUObject.dll!UObject::CallFunction() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\ScriptCore.cpp:927] [2020.05.08-16.56.04:775][310]LogWindows: Error: [Callstack] 0x00007ffa460c2fd3 UE4Editor-CoreUObject.dll!UObject::ProcessContextOpcode() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\ScriptCore.cpp:2796] [2020.05.08-16.56.04:775][310]LogWindows: Error: [Callstack] 0x00007ffa460c560d UE4Editor-CoreUObject.dll!ProcessLocalScriptFunction() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\ScriptCore.cpp:997] [2020.05.08-16.56.04:775][310]LogWindows: Error: [Callstack] 0x00007ffa46093aaa UE4Editor-CoreUObject.dll!ProcessScriptFunction<void (__cdecl*)(UObject *,FFrame &,void *)>() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\ScriptCore.cpp:828] [2020.05.08-16.56.04:775][310]LogWindows: Error: [Callstack] 0x00007ffa460c5252 UE4Editor-CoreUObject.dll!ProcessLocalFunction() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\ScriptCore.cpp:1058] [2020.05.08-16.56.04:775][310]LogWindows: Error: [Callstack] 0x00007ffa460c560d UE4Editor-CoreUObject.dll!ProcessLocalScriptFunction() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\ScriptCore.cpp:997] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ffa460c4b14 UE4Editor-CoreUObject.dll!UObject::ProcessInternal() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\ScriptCore.cpp:1085] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ffa45e50ab4 UE4Editor-CoreUObject.dll!UFunction::Invoke() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\Class.cpp:5542] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ffa460c4643 UE4Editor-CoreUObject.dll!UObject::ProcessEvent() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\ScriptCore.cpp:1916] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ffa01e79fc5 UE4Editor-Engine.dll!AActor::ProcessEvent() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Engine\Private\Actor.cpp:798] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ffa030347c4 UE4Editor-Engine.dll!FInputActionUnifiedDelegate::Execute() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Engine\Classes\Components\InputComponent.h:302] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ffa030603fe UE4Editor-Engine.dll!UPlayerInput::ProcessInputStack() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Engine\Private\UserInterface\PlayerInput.cpp:1321] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ffa02b687b8 UE4Editor-Engine.dll!APlayerController::ProcessPlayerInput() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Engine\Private\PlayerController.cpp:2567] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ffa02b7bfe4 UE4Editor-Engine.dll!APlayerController::TickPlayerInput() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Engine\Private\PlayerController.cpp:4580] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ffa02b6684b UE4Editor-Engine.dll!APlayerController::PlayerTick() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Engine\Private\PlayerController.cpp:2228] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ffa02b7a4b1 UE4Editor-Engine.dll!APlayerController::TickActor() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Engine\Private\PlayerController.cpp:4726] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ffa01e59464 UE4Editor-Engine.dll!FActorTickFunction::ExecuteTick() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Engine\Private\Actor.cpp:171] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ffa02f1556f UE4Editor-Engine.dll!FTickFunctionTask::DoTask() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Engine\Private\TickTaskManager.cpp:283] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ffa02f1a5c7 UE4Editor-Engine.dll!TGraphTask<FTickFunctionTask>::ExecuteTask() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Core\Public\Async\TaskGraphInterfaces.h:849] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ffa04b188d8 UE4Editor-Core.dll!FNamedTaskThread::ProcessTasksNamedThread() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Core\Private\Async\TaskGraph.cpp:692] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ffa04b18ba3 UE4Editor-Core.dll!FNamedTaskThread::ProcessTasksUntilQuit() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Core\Private\Async\TaskGraph.cpp:587] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ffa04b2f127 UE4Editor-Core.dll!FTaskGraphImplementation::WaitUntilTasksComplete() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Core\Private\Async\TaskGraph.cpp:1478] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ffa02f365b2 UE4Editor-Engine.dll!FTickTaskSequencer::ReleaseTickGroup() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Engine\Private\TickTaskManager.cpp:558] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ffa02f3b87a UE4Editor-Engine.dll!FTickTaskManager::RunTickGroup() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Engine\Private\TickTaskManager.cpp:1523] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ffa026fbbdf UE4Editor-Engine.dll!UWorld::RunTickGroup() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Engine\Private\LevelTick.cpp:783] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ffa02706477 UE4Editor-Engine.dll!UWorld::Tick() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Engine\Private\LevelTick.cpp:1558] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ffa0034a737 UE4Editor-UnrealEd.dll!UEditorEngine::Tick() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Editor\UnrealEd\Private\EditorEngine.cpp:1693] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ffa00c20056 UE4Editor-UnrealEd.dll!UUnrealEdEngine::Tick() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Editor\UnrealEd\Private\UnrealEdEngine.cpp:414] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ff7e6a77800 UE4Editor.exe!FEngineLoop::Tick() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Launch\Private\LaunchEngineLoop.cpp:4850] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ff7e6a8ba7c UE4Editor.exe!GuardedMain() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Launch\Private\Launch.cpp:169] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ff7e6a8bb5a UE4Editor.exe!GuardedMainWrapper() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:137] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ff7e6a9e31d UE4Editor.exe!WinMain() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:268] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ff7e6aa145a UE4Editor.exe!__scrt_common_main_seh() [d:\agent\_work\5\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ffa7be67bd4 KERNEL32.DLL!UnknownFunction [] [2020.05.08-16.56.04:776][310]LogWindows: Error: [Callstack] 0x00007ffa7c2cce51 ntdll.dll!UnknownFunction []
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-92909 in the post.