prevent php-warning in timesrooms, fixes #4614

Closes #4614

Merge request studip/studip!3427

app/controllers/course/timesrooms.php

@@ -910,11 +910,13 @@ class Course_TimesroomsController extends AuthenticatedController
     {
         $appointment_ids = [];
 
+        if (!empty($_SESSION['_checked_dates'])) {
             foreach ($_SESSION['_checked_dates'] as $appointment_id) {
                 if (CourseDate::exists($appointment_id)) {
                     $appointment_ids[] = $appointment_id;
                 }
             }
+        }
 
         if (!$appointment_ids) {
             PageLayout::postError(_('Es wurden keine gültigen Termin-IDs übergeben!'));
@@ -951,6 +953,7 @@ class Course_TimesroomsController extends AuthenticatedController
      */
     private function unDeleteStack($cycle_id = '')
     {
+        if (!empty($_SESSION['_checked_dates'])) {
             foreach ($_SESSION['_checked_dates'] as $id) {
                 $ex_termin = CourseExDate::find($id);
                 if ($ex_termin === null) {
@@ -965,6 +968,7 @@ class Course_TimesroomsController extends AuthenticatedController
                     ));
                 }
             }
+        }
 
         $this->relocate('course/timesrooms/index', ['contentbox_open' => $cycle_id]);
     }
@@ -1007,12 +1011,14 @@ class Course_TimesroomsController extends AuthenticatedController
         $cancel_comment = trim(Request::get('cancel_comment'));
         $cancel_send_message = Request::int('cancel_send_message');
 
+        if (!empty($_SESSION['_checked_dates'])) {
             foreach ($_SESSION['_checked_dates'] as $id) {
                 $termin = CourseDate::find($id);
                 if ($termin) {
                     $deleted_dates[] = $this->deleteDate($termin, $cancel_comment);
                 }
             }
+        }
 
         if ($cancel_send_message && $cancel_comment != '' && count($deleted_dates) > 0) {
             $snd_messages = raumzeit_send_cancel_message($cancel_comment, $deleted_dates);
@@ -1037,7 +1043,7 @@ class Course_TimesroomsController extends AuthenticatedController
         $groups_changed  = false;
         $singledates     = [];
 
-        if (is_array($_SESSION['_checked_dates'])) {
+        if (!empty($_SESSION['_checked_dates'])) {
             foreach ($_SESSION['_checked_dates'] as $singledate_id) {
                 $singledate = CourseDate::find($singledate_id);
                 if (!isset($singledate)) {
@@ -1229,12 +1235,14 @@ class Course_TimesroomsController extends AuthenticatedController
         }
 
         $appointments = [];
+        if (!empty($_SESSION['_checked_dates'])) {
             foreach ($_SESSION['_checked_dates'] as $appointment_id) {
                 $appointment = CourseDate::find($appointment_id);
                 if ($appointment) {
                     $appointments[] = $appointment;
                 }
             }
+        }
 
         if (!$appointments) {
             PageLayout::postError(_('Es wurden keine gültigen Termine übergeben!'));