ensure booking is valid before updating event, fixes #1300

Closes #1300

Merge request studip/studip!798

lib/models/ConsultationSlot.php

@@ -204,11 +204,19 @@ class ConsultationSlot extends SimpleORMap
 
         // If no range is associated, remove the event
         if (!$this->block->range) {
-            return $this->removeEvent();
+            $this->removeEvent();
+            return;
         }
 
-        if (count($this->bookings) === 0 && !$this->block->calendar_events) {
-            return $this->removeEvent();
+        $bookings = $this->bookings->filter(function (ConsultationBooking $booking) {
+            return !$booking->isDeleted()
+                && $booking->user;
+        });
+
+
+        if (count($bookings) === 0 && !$this->block->calendar_events) {
+            $this->removeEvent();
+            return;
         }
 
         $event = $this->event;
@@ -221,11 +229,11 @@ class ConsultationSlot extends SimpleORMap
 
         setTempLanguage($this->block->range_id);
 
-        if (count($this->bookings) > 0) {
+        if (count($bookings) > 0) {
             $event->category_intern = 1;
 
-            if (count($this->bookings) === 1) {
-                $booking = $this->bookings->first();
+            if (count($bookings) === 1) {
+                $booking = $bookings->first();
 
                 $event->summary = sprintf(
                     _('Termin mit %s'),
@@ -235,9 +243,9 @@ class ConsultationSlot extends SimpleORMap
             } else {
                 $event->summary = sprintf(
                     _('Termin mit %u Personen'),
-                    count($this->bookings)
+                    count($bookings)
                 );
-                $event->description = implode("\n\n----\n\n", $this->bookings->map(function ($booking) {
+                $event->description = implode("\n\n----\n\n", $bookings->map(function ($booking) {
                     return "- {$booking->user->getFullName()}:\n{$booking->reason}";
                 }));
             }