Fix critical error in previous commit

src/pretix/api/views/event.py

@@ -244,13 +244,14 @@ class SubEventViewSet(ConditionalListView, viewsets.ModelViewSet):
         )
 
     def perform_update(self, serializer):
-        if serializer.data == self.get_serializer(instance=serializer.instance).data:
+        original_data = self.get_serializer(instance=serializer.instance).data
+        super().perform_update(serializer)
+
+        if serializer.data == original_data:
             # Performance optimization: If nothing was changed, we do not need to save or log anything.
             # This costs us a few cycles on save, but avoids thousands of lines in our log.
             return
 
-        super().perform_update(serializer)
-
         serializer.instance.log_action(
             'pretix.subevent.changed',
             user=self.request.user,

src/pretix/api/views/item.py

@@ -65,11 +65,14 @@ class ItemViewSet(ConditionalListView, viewsets.ModelViewSet):
         return ctx
 
     def perform_update(self, serializer):
-        if serializer.data == self.get_serializer(instance=serializer.instance).data:
+        original_data = self.get_serializer(instance=serializer.instance).data
+
+        serializer.save(event=self.request.event)
+
+        if serializer.data == original_data:
             # Performance optimization: If nothing was changed, we do not need to save or log anything.
             # This costs us a few cycles on save, but avoids thousands of lines in our log.
             return
-        serializer.save(event=self.request.event)
         serializer.instance.log_action(
             'pretix.event.item.changed',
             user=self.request.user,
@@ -456,14 +459,17 @@ class QuotaViewSet(ConditionalListView, viewsets.ModelViewSet):
         return ctx
 
     def perform_update(self, serializer):
-        if serializer.data == self.get_serializer(instance=serializer.instance).data:
-            # Performance optimization: If nothing was changed, we do not need to save or log anything.
-            # This costs us a few cycles on save, but avoids thousands of lines in our log.
-            return
+        original_data = self.get_serializer(instance=serializer.instance).data
 
         current_subevent = serializer.instance.subevent
         serializer.save(event=self.request.event)
         request_subevent = serializer.instance.subevent
+
+        if serializer.data == original_data:
+            # Performance optimization: If nothing was changed, we do not need to save or log anything.
+            # This costs us a few cycles on save, but avoids thousands of lines in our log.
+            return
+
         serializer.instance.log_action(
             'pretix.event.quota.changed',
             user=self.request.user,