pass existing opqs into filter_qs

Co-authored-by: Richard Schreiber <schreiber@pretix.eu>

src/pretix/control/forms/item.py

@@ -353,13 +353,9 @@ class QuestionAnswerFilterForm(forms.Form):
                 raise forms.ValidationError(_("Selected subevent isn't part of the date range."))
         return cleaned_data
 
-    def filter_qs(self):
+    def filter_qs(self, opqs):
         fdata = self.cleaned_data
 
-        opqs = OrderPosition.objects.filter(
-            order__event=self.event,
-        )
-
         subevent = fdata.get('subevent', None)
         date_range = fdata.get('date_range', None)
 

src/pretix/control/views/item.py

@@ -671,10 +671,11 @@ class QuestionView(EventPermissionRequiredMixin, ChartContainingView, DetailView
         return QuestionAnswerFilterForm(event=self.request.event, data=self.request.GET)
 
     def get_answer_statistics(self):
-        if not self.filter_form.is_valid():
-            return
-
-        opqs = self.filter_form.filter_qs()
+        opqs = OrderPosition.objects.filter(
+            order__event=self.event,
+        )
+        if self.filter_form.is_valid():
+            opqs = self.filter_form.filter_qs(opqs)
 
         qs = QuestionAnswer.objects.filter(
             question=self.object, orderposition__isnull=False,