SlateDialogs does not block user from setting a folder as the uproject in UFE

Users are able to set a folder as the project using SlateDialogs in Unreal Frontend on the Linux machine.

1. Open UnrealFrontend
2. Select the Project drop down button
3. Select Browse in the drop down menu
4. Select the Projects button
5. Select the Open button

RESULT:
Users are able to specify a folder when selecting a project to launch through UnrealFrontend on the Linux machine.

EXPECTED:
I expected to see:

• a red ! error icon next to the Project setting in the Project Launcher tab when there is not a valid uproject file specified
• a error message pop up when trying to set something that is not a uproject file
• the launch buttons greyed out and inactive when there is not a valid uproject file specified