We first need a thunderbird package that actually displays a window.
Just tryied with your spec. Running with -g shows me
[Switching to Thread 16384 (LWP 9702)] 0x4004ab40 in js_AllocStack () from /usr/lib/mozilla-thunderbird-0.3/libmozjs.so
Looks like it's catched and thunderbird exits "normally" when it occurs.
