mail_index_keywords_create_from_indexes(): Don't crash with 64bit systems if there are only 0 keywords.
mail_index_keywords_create_from_indexes(): Don't crash with 64bit systems if there are only 0 keywords.

damoxc/dovecot,damoxc/dovecot,damoxc/dovecot,Distrotech/dovecot,Distrotech/dovecot,damoxc/dovecot,damoxc/dovecot,Distrotech/dovecot,Distrotech/dovecot,Distrotech/dovecot