Sanity check return value of UIDVALIDTY response
Sanity check return value of UIDVALIDTY response

We have a reported case where response('UIDVALIDITY') returned [None]
which results in an ugly non-intuitive crash. Sanity check and report
something nicer.

Signed-off-by: Sebastian Spaeth <98dcb2717ddae152d5b359c6ea97e4fe34a29d4c@SSpaeth.de>

frioux/offlineimap,frioux/offlineimap