Crash Bug #2665: Crash trying to create a pocket from an unattached sketch (Testers Needed)

[Kunda1]

issue #2665: Crash trying to create a pocket from an unattached sketch

I was able to reproduce the crash twice, but I couldn't find a way to get it reliable.

The point is that the behaviour has changed when trying to create a pocket from an unattached sketch.
In v0.16 and older it pops up a dialog that the sketch has no support face and does nothing further. In v0.17 it first opens the task panel (but the 3d view becomes empty) and after pressing the OK button the above error message appears.

Now I was able to get the crash:
* open two documents
* create a sketch on the one
* while the task dialog is open switch to the other document
* closing the task panel now doesn't destroy the invalid pocket feature

Now after some wild clicking it crashed for me two times but wasn't able to locate the reason.