x11: Don't assume valid type
If we get an invalid TARGETS reply, we might not have a valid 'type', which ends up as NULL and segs in the g_str_equal.
(This is probably fallout from my fix 506566b6, which I still can't reproduce reliably, so the last one just moved the seg a bit further along, and we still don't know who is sending a bad TARGETS).
This corresponds to: https://bugzilla.redhat.com/show_bug.cgi?id=2062143