[Dovecot] imap crash during URLFETCH

[Mike Abbott]

>> without having set *mpurl_r to NULL
> 
> Right, fixed: http://hg.dovecot.org/dovecot-2.2/rev/24aa10efe132

That fixes it, thanks, but I wonder if it's incomplete?  I notice that these also sometimes don't set *mpurl_r:
imap_msgpart_url_create()
imap_msgpart_url_parse()
imap_urlauth_fetch()

That last one in particular is called from imap_urlauth_fetch_local() in the same way as the one you fixed.