Add null check for ownerless tickets

cron/calendar_reminders.php

@@ -121,7 +121,7 @@ $sql = "SELECT `ticket`.`id` AS `id`, `ticket`.`trackid` AS `trackid`, `ticket`.
     `ticket`.`custom17` AS `custom17`, `ticket`.`custom18` AS `custom19`, `ticket`.`custom19` AS `custom19`, `ticket`.`custom20` AS `custom20`,
     `ticket`.`html` AS `html`
     FROM `" . hesk_dbEscape($hesk_settings['db_pfix']) . "tickets` AS `ticket`
-    INNER JOIN `" . hesk_dbEscape($hesk_settings['db_pfix']) . "users` AS `user`
+    LEFT JOIN `" . hesk_dbEscape($hesk_settings['db_pfix']) . "users` AS `user`
         ON `ticket`.`owner` = `user`.`id`
     WHERE `due_date` IS NOT NULL
         AND `due_date` <= NOW()

inc/email_functions.inc.php

@@ -339,7 +339,9 @@ function mfh_sendOverdueTicketReminder($ticket, $users, $modsForHesk_settings) {
     $htmlMessage = hesk_processMessage($htmlMessage, $ticket, 1, 1, 0, $modsForHesk_settings, 1);
 
     $emails = [];
-    $emails[] = $ticket['user_email'];
+    if ($ticket['user_email'] != NULL) {
+        $emails[] = $ticket['user_email'];
+    }
     foreach ($users as $user) {
         if ($user['email'] != $ticket['user_email']
             && ($user['isadmin'] || strpos($user['categories'], $ticket['category']) !== false)) {