Fix crash when trying to export zero files.
Fix crash when trying to export zero files.

Fixes crash that happened while exporting if zero files were selected
and adds more error handling to EditorExportPlatform class.

(cherry picked from commit 15656d4182907183d9a60a116f88187bae1e94a9)

ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot