Starting Line 271 of email_api.php:

Exclude users who have this notification type turned off

        if ( $t_pref_field ) {
            $t_notify = user_pref_get_pref( $t_id, $t_pref_field );
            if ( OFF == $t_notify ) {
                unset( $t_recipients[$t_id] );
                continue;
            } else {
                # Users can define the severity of an issue before they are emailed for
                # each type of notification
                $t_min_sev_pref_field = $t_pref_field . '_minimum_severity';
                $t_min_sev_notify     = user_pref_get_pref( $t_id, $t_min_sev_pref_field );
                $t_bug_severity       = bug_get_field( $p_bug_id, 'severity' );

                if ( $t_bug_severity < $t_min_sev_notify ) {
                    unset( $t_recipients[$t_id] );
                    continue;
                }
            }

START MISSING ELSE STATEMENT

        } else {
            unset( $t_recipients[$t_id] );
            continue;

END MISSING ELSE STATEMENT

        }