Nativized builds will crash on launch if a non-nativized Blueprint references a User-Defined Enum property in a nativized Blueprint.

EDL-related crash occurs on launch of exclusively-nativized build where a non-nativized BP references a User-Defined Enum property in a nativized BP.

Related to [Link Removed], but this is a parallel issue.

1. Launch UE4 editor and create a new (blank) C++ project.
2. Create a new User-Defined Enum (TestEnum) and save it.
3. Create a new Blueprint class based on Actor (MyNativizedBP). Double-click to edit it.
4. In "Class Settings," tick the "Nativize" checkbox.
5. Add a new variable of type 'TestEnum' (MyEnumVar).
6. Compile and save the Blueprint, then close the Blueprint editor.
7. Create another new Blueprint class based on Actor (MyNonNativizedBP). Double-click to edit it.
8. Add a new Object Reference variable of type 'MyNativizedBP' (call it MyBP) and click the eye icon to make it editable.
9. Drag the variable into the event graph and add a 'Get' node.
10. Drag off the 'Get' node's output pin and add a 'Get MyEnumVar' node.
11. Drag off the 'Get MyEnumVar' node's output pin and add a 'Print String' node.
12. Wire up the 'Print String' node to the BeginPlay event node.
13. Drag an instance of both Blueprints into the current level. Set the 'MyBP' reference on the 'MyNonNativizedBP' instance to the 'MyNativizedBP' instance.
14. Save the map (NewMap). PIE, and note that the enum label is printed out. Exit PIE.
15. In Project Settings->Packaging, set "Nativization mode" to "Exclusive."
16. In Project Settings->Maps and Modes, set 'NewMap' as the default gameplay map.
17. Choose File->Package Project->Windows->Win64 and wait for packaging to finish.
18. Double-click the packaged EXE to launch. Note that a crash will result:

LogWindows: Error: Missing import of (/Game/MyNonNativizedBP): MyEnumVar in Package /Game/MyNativizedBP was not found, but the package exists.