If cached message part showed header's size to be smaller than in reality, return "broken" instead of assert-crashing.
If cached message part showed header's size to be smaller than in reality,
return "broken" instead of assert-crashing.

LTD-Beget/dovecot,LTD-Beget/dovecot,LTD-Beget/dovecot,LTD-Beget/dovecot,LTD-Beget/dovecot