requested changes from review

moto/cloudformation/models.py

@@ -678,7 +678,7 @@ class CloudFormationBackend(BaseBackend):
     def list_stack_resources(self, stack_name_or_id):
         stack = self.get_stack(stack_name_or_id)
         if stack is None:
-            return []
+            return None
         return stack.stack_resources
 
     def delete_stack(self, name_or_stack_id):

moto/cloudformation/responses.py

@@ -229,7 +229,7 @@ class CloudFormationResponse(BaseResponse):
         stack_name_or_id = self._get_param("StackName")
         resources = self.cloudformation_backend.list_stack_resources(stack_name_or_id)
 
-        if not resources:
+        if resources is None:
             raise ValidationError(stack_name_or_id)
 
         template = self.response_template(LIST_STACKS_RESOURCES_RESPONSE)