Could never reproduce it consistently, and I'm always hesitent to file a bug without decent repro steps. Also, it seems to have been fixed in latest... maybe. Again, if I can't reproduce it consistently, I can't say if it's fixed or not.
So what I do in these situations is go to about:crashes, click on the appropriate crash id and look under the Related Bugs section. If there’s been a bug filed with the same signature then it’ll appear there. Alternatively, if it’s not been filed already you could click on ‘More Reports’ and look at the number of crashes. If it looks like a few you might want to file it with just the signature and no steps to reproduce; sometimes a signature and backtrace alone is enough to diagnose and fix (e.g. this one I filed recently: https://bugzilla.mozilla.org/show_bug.cgi?id=1163945 ).