Dear Maintainer,

When I attempted to delete a message in icedove it crashed. This
happens fairly often, but is not deterministic, i.e. attempting to delete a
message may crash icedove, but on the next run deleting the message
works fine.

A stack trace is attached below. This particular crash happened while
running in safe mode and in the debugger, with the command line:

/usr/lib/icedove/run-mozilla.sh -g /usr/lib/icedove/icedove-bin --safe-mode 2>&1 | tee /tmp/icedove-gdb-$(dpkg-query -s icedove | grep Version | cut -f3 -d":").log.4