Redirect to next step if AddOnsStep would show up empty (Z#23167007) (#4530)

src/pretix/presale/checkoutflow.py

@@ -47,6 +47,7 @@ from django.db import models
 from django.db.models import Count, F, Q, Sum
 from django.db.models.functions import Cast
 from django.http import HttpResponseNotAllowed, JsonResponse
+from django.shortcuts import redirect
 from django.utils import translation
 from django.utils.functional import cached_property
 from django.utils.translation import (
@@ -659,6 +660,8 @@ class AddOnsStep(CartMixin, AsyncAction, TemplateFlowStep):
         self.request = request
         if 'async_id' in request.GET and settings.HAS_CELERY:
             return self.get_result(request)
+        if len(self.forms) == 0 and len(self.cross_selling_data) == 0:
+            return redirect(self.get_next_url(request))
         return TemplateFlowStep.get(self, request)
 
     def _clean_category(self, form, category):