actofgod: Simplify fmtflags()'s error checking

Permit finding length by passing no buffer.  Not currently used.

Oops at most once.

Signed-off-by: Markus Armbruster <armbru@pond.sub.org>
Update change log again for 4.3.32

Signed-off-by: Markus Armbruster <armbru@pond.sub.org>