** If sequence is new, or zero flag is set, then first
** clear the bit for this sequence from all messages.
*/
- if (new_seq || zero) {
+ if (mp->nummsg>0 && (new_seq || zero)) {
for (msgnum = mp->lowmsg; msgnum <= mp->hghmsg; msgnum++)
clear_sequence(mp, i, msgnum);
}