Added backend filter rule check

(Redmine issue: #7625)

lib/hawat/blueprints/filters/__init__.py

@@ -413,6 +413,8 @@ class CreateView(HTMLMixin, SQLAlchemyMixin, ItemCreateView):  # pylint: disable
 
     def do_before_action(self, item):  # pylint: disable=locally-disabled,no-self-use,unused-argument
         process_rule(item)
+        # Check if the filter rule is valid.
+        to_tree(item.filter)
 
     def do_before_response(self, **kwargs):
         item = self.response_context.get('item', None)
@@ -518,6 +520,8 @@ class CreateForView(HTMLMixin, SQLAlchemyMixin,
 
     def do_before_action(self, item):  # pylint: disable=locally-disabled,no-self-use,unused-argument
         process_rule(item)
+        # Check if the filter rule is valid.
+        to_tree(item.filter)
 
     def do_before_response(self, **kwargs):
         item = self.response_context.get('item', None)
@@ -608,6 +612,8 @@ class UpdateView(HTMLMixin, SQLAlchemyMixin, ItemUpdateView):  # pylint: disable
 
     def do_before_action(self, item):  # pylint: disable=locally-disabled,no-self-use,unused-argument
         process_rule(item)
+        # Check if the filter rule is valid.
+        to_tree(item.filter)
 
     def do_before_response(self, **kwargs):
         item = self.response_context['item']