[fixed] Wings_crash.dump - function_clause

[dgud]

Micheus, I think it is related to wings_wm:grab() and ungrab(), since 2.0.0 every
grab must be followed by an ungrab, otherwise wings gets confused.

I have added ungrab in a couple of places in 2.1.6, where it was missing,
but the tweak code is so hard to follow that something is still broken there.

I have noticed it maybe once or twice after my fixes, but have not been able to repeat it after adding debug printouts, but I think I have fixed most of the issues. But it's always the last one that is the hardest to fix right.

What does wings_io_wx.beam patch do?

Hank what camera mode do you use?
Is that a clean wings-2.1.6 install?
OS Windows/Linux/Mac ?
Are you using any other software when modelling that might want to steal the mouse input?