[BUG][EDITOR] Corrupt file error crashes Editor / requires Task Manager to close

[WillLem]

Perhaps not a bug as such, but when opening a level which contains a missing/corrupt file, the following dialog appears:



This is fine, but there is no way to exit past the dialog or close the Editor from its own instance; the Editor must be force-closed via Task Manager when this happens.

Suggestion: allow Editor to load placeholder graphic for missing files (similar to the Player's ability to do this) so that this dialog can be closed and the Editor can then either remain open or be closed/restarted from its own instance.