dbmail-util -My segfault

Hello

in maintenance.c in
int do_migrate(int migrate_limit)

there is no m != NULL check after

m = dbmail_message_retrieve(m, id);

so it segfaults in "if(! dm_message_store(m)) {" if m == NULL.

Yes, I guess db probably slightly broken, but dbmail-util cannot find
and fix these errors.