It was one time and I couldn't reproduce it again.
I have a backtrace, but since it's not always reproducable is it ok to write bug reports reporting crashes like this?

Just curious. Thanks as always.

If you have a backtrace, it's always possible we might find a way to figure out what was going, so, yes, please do report this. Backtraces also prove that there's a bug -- unless the backtrace ends up deep in Qt or in the GPU drivers, but that's for us to worry about