Fix FilteredListView to allow non paginated views

src/core/views/list_views.py

@@ -30,6 +30,8 @@ class FilteredListView(ListView):
         """
         try:
             paginate_by = self.request.GET.get('paginate_by', self.paginate_by)
+            if paginate_by is None:
+                return self.paginate_by
             paginate_by = int(paginate_by)
         except ValueError:
             if str(paginate_by).lower() == 'all':