It probably means it's a Heisenbug: it's triggered by some specific
memory layout, and that changes under the debugger.
Yeah, I hate those kinds of bugs.. I am good for stumbling across those :P
Are you still able to trigger the abort when running not under GDB?
If that's gone as well, try rebuilding Emacs by touching src/config.h
or somesuch, then try again.
Same. The crash is gone.
I'll still leave that emacsclient session running with gdb attached - I hope to catch this Heisenbug. Funny, I see like 6-7 crashes in the past week. And the moment I report it, it gets scared and goes away.