Reproduction:
1) Create a new issue
2) Get a bitmap file (.bmp), and rename it test.jpg (yes, I know this qualifies as silly)
3) Attach the now silly image to your new issue from #1
4) witness the log file explode with stack traces, and see the broken thumbnails on the issue

I'm not asking you guys to invent smarter users, we're working on them over here, but the thumbnailing code should handle this error more gracefully as it is user input and the principle of the internet is to "be liberal in what accept".

You should expect users to upload all manner of mislabeled or non-conforming junk, and not error out because of it. It might be a valid attachment, and you're just inferring too much from the name