notmuch 0.6: notmuch new dies with std::terminate

[Robin Green]

Some time after upgrading to notmuch 0.6, notmuch new suddenly started
failing, with this backtrace: (this is on DragonFly BSD)

Program terminated with signal 6, Aborted.
#0  0x00000008017bde18 in kill () from /usr/lib/libc.so.7
(gdb) bt
#0  0x00000008017bde18 in kill () from /usr/lib/libc.so.7
#1  0x000000080183779d in raise () from /usr/lib/libc.so.7
#2  0x0000000801837195 in abort () from /usr/lib/libc.so.7
#3  0x000000080150c9c1 in __gnu_cxx::__verbose_terminate_handler() () from /usr/lib/gcc44/libstdc++.so.9
#4  0x0000000801511047 in __cxxabiv1::__terminate(void (*)()) () from /usr/lib/gcc44/libstdc++.so.9
#5  0x000000080151107c in std::terminate() () from /usr/lib/gcc44/libstdc++.so.9
#6  0x0000000801510fe4 in __cxa_throw () from /usr/lib/gcc44/libstdc++.so.9
#7  0x0000000801adac99 in Xapian::Document::Internal::remove_term (this=<value optimized out>, tname=<value optimized out>)
    at api/omdocument.cc:404
#8  0x000000080086d020 in _notmuch_message_remove_term (message=0x8007719d0, prefix_name=0x800871cc9 "tag", 
    value=0x800871be0 "draft") at lib/message.cc:915
#9  0x000000080086d239 in notmuch_message_remove_tag (message=0x8007719d0, tag=0x800871be0 "draft") at lib/message.cc:974
#10 0x000000080086d421 in notmuch_message_maildir_flags_to_tags (message=0x8007719d0) at lib/message.cc:1030
#11 0x000000000040976d in add_files_recursive (notmuch=0x8007a02f0, path=0x8008003a8 "/home/greenrd/Mail/sent/cur", 
    state=0x7ffffffff800) at notmuch-new.c:459
#12 0x0000000000409236 in add_files_recursive (notmuch=0x8007a02f0, path=0x8007f0650 "/home/greenrd/Mail/sent", 
    state=0x7ffffffff800) at notmuch-new.c:330
#13 0x0000000000409236 in add_files_recursive (notmuch=0x8007a02f0, path=0x8007f0378 "/home/greenrd/Mail", 
    state=0x7ffffffff800) at notmuch-new.c:330
#14 0x0000000000409cb7 in add_files (notmuch=0x8007a02f0, path=0x8007f0378 "/home/greenrd/Mail", state=0x7ffffffff800)
    at notmuch-new.c:625
#15 0x000000000040a61c in notmuch_new_command (ctx=0x8006c02e8, argc=0, argv=0x7ffffffff988) at notmuch-new.c:866
#16 0x0000000000407038 in main (argc=2, argv=0x7ffffffff978) at notmuch.c:632

I'm not a C++ programmer, but what I notice that's odd about this is
that the exception *should* be caught by a catch, but isn't being.

Because I couldn't figure out what is going wrong here, I switched back
to notmuch 0.5, which worked.

This may have to do with some errors I saw from notmuch search about a
temporary draft file created by emacs no longer existing. Or that may be
unrelated - I have no idea.