4.2: Crash when restoring session with .ui file open from Welcome screen

On 4.2.2 and earlier versions (I think all 4.x during last year).

If you load work space as usually, open widget designer (maybe switch to cpp file) and turn off creator, then you will not be able to load that workspace back. It will crash on next load (with like 80% chance. sometimes it still loads, but most likelly not).

However I have creator_tabbed_editor
https://github.com/alexzk1/qtcreator-tabbededitor-plugin
(shows files in tabs) enabled. Don't think it's related but who knows.

So to recap, if you left opened widget designer, most likelly you will not be able to load workspace back (but can open project in fresh space).

Because it happens with chances, not 100% (but near), it could be some sync issue, i use: Linux, LxQt desktop (had crashes prior on KDE as well), i7, 8 cores.