Fix obscure crash in log entry view

src/pretix/control/logdisplay.py

@@ -440,7 +440,7 @@ def pretixcontrol_logentry_display(sender: Event, logentry: LogEntry, **kwargs):
             bleach.clean(logentry.parsed_data.get('msg'), tags=[], strip=True)
         )
 
-    if logentry.action_type.startswith('pretix.event.checkin'):
+    if sender and logentry.action_type.startswith('pretix.event.checkin'):
         return _display_checkin(sender, logentry)
 
     if logentry.action_type == 'pretix.control.views.checkin':

src/pretix/control/views/organizer.py

@@ -751,7 +751,9 @@ class DeviceLogView(OrganizerDetailViewMixin, OrganizerPermissionRequiredMixin,
         qs = LogEntry.objects.filter(
             device_id=self.device
         ).select_related(
-            'user', 'content_type', 'api_token', 'oauth_application', 'device', 'event'
+            'user', 'content_type', 'api_token', 'oauth_application',
+        ).prefetch_related(
+            'device', 'event'
         ).order_by('-datetime')
         return qs