I was getting seemingly random crashes when exiting, but have tracked down the problem...
The crash occurs if you quit while nebulae images are being loaded, i.e. quit while the "loading nebulae" progress bar is visible. This is running 0.10.5 on Windows, but it will also affect older versions. (I wouldn't be surprised if this is the cause of some of the other crash reports, or that they were at least getting a combination of problems). I can't repeat on Linux, but that's most likely due to the images loading so fast I can't quit at the same time - too old, too slow :)
The problem originates in:
Removing this eliminates the crash.
I haven't had a chance to look at why this is happening (or exactly what is happening during loading of images) but someone familiar with this section of code can probably fix it easily. (As a side note, I did try adding a check for the app closing here, but Qt never reported that it was in fact in the process of closing as I would have expected it to - need to look into that.)