EventPluginSignal: Call core plugins even when no event is given

src/pretix/base/models/log.py

@@ -37,7 +37,8 @@ class LogEntry(models.Model):
     def display(self):
         from ..signals import logentry_display
 
-        for receiver, response in logentry_display.send(self.event, logentry=self):
-            if response:
-                return response
+        if self.event:
+            for receiver, response in logentry_display.send(self.event, logentry=self):
+                if response:
+                    return response
         return self.action_type

src/pretix/base/signals.py

@@ -22,7 +22,8 @@ class EventPluginSignal(django.dispatch.Signal):
 
         sender is required to be an instance of ``pretix.base.models.Event``.
         """
-        assert isinstance(sender, Event)
+        if sender and not isinstance(sender, Event):
+            raise ValueError("Sender needs to be an event.")
 
         responses = []
         if not self.receivers or self.sender_receivers_cache.get(sender) is NO_RECEIVERS:
@@ -44,7 +45,7 @@ class EventPluginSignal(django.dispatch.Signal):
                 searchpath, mod = searchpath.rsplit(".", 1)
 
             # Only fire receivers from active plugins and core modules
-            if (searchpath, mod) in settings.CORE_MODULES or (app and app.name in sender.get_plugins()):
+            if (searchpath, mod) in settings.CORE_MODULES or (sender and app and app.name in sender.get_plugins()):
                 if not hasattr(app, 'compatibility_errors') or not app.compatibility_errors:
                     response = receiver(signal=self, sender=sender, **named)
                     responses.append((receiver, response))