As long as this does not change in GTK+ and no workaround is possible in
Emacs, I (sadly) think you should seriously consider disabling detaching
the tool bar in the GTK+ build. When used in conjunction with --daemon
it is a ticking time bomb for data loss because of the crash it causes.
I don't make this suggestion lightly, since detaching the tool bar is to
me an acceptable workaround for the very annoying shrinking frame bug
(see bug#3195), but precluding a crash and possible data loss should
probably take precedence over avoiding annoyance.