Blender Git Loki

Fix crash opening maximized File Browser from Asset Browser

If Preferences > Interface > Temporary Editors > File Browser is set to
"Maximized Area", opening a File Browser from an Asset Browser would
cause the new maximized editor to be an Asset Browser. Exiting it again
would crash.

This fixes the wrong behavior and the crash. There's still an issue with
exiting the editor again, it stays a File Browser then and doesn't go
back to being an Asset Browser. That's to be fixed separately.