Crash when moving mixer channels to left/right

[badosu]

Sometimes you are able to cause a Segmentation Fault when using the "Move Right"/"Move Left" functionality on mixer channels.

I was not able to identify how to reproduce this error deterministically, but you should be able to trigger this just moving nearby channels at the rightmost part of the mixer.

The backtrace shows that this is the offending line:

lmms/src/gui/widgets/FxLine.cpp

Line 208 in 4043868

contextMenu->exec( QCursor::pos() );

Full backtrace here: https://gist.github.com/badosu/54bf4c6cd2d504daaab0

[tresf]

#1545

[badosu]

@tresf I don't know if this is exactly the same bug. But may be related.

[tresf]

@tresf I don't know if this is exactly the same bug. But may be related.

Yeah, I just wanted to link them in case they are. I should have put a contextual message with that tag. 🐓

[lukas-w]

Same issue as #872