fix(insights): Fix breakdown value zero (#23387)

posthog/hogql_queries/insights/funnels/funnel_trends.py

@@ -74,7 +74,7 @@ def _format_results(self, results) -> list[dict[str, Any]]:
 
             if breakdown_clause:
                 breakdown_value = period_row[-1]
-                if breakdown_value is None or breakdown_value == [None]:
+                if breakdown_value in (None, [None], 0):
                     serialized_result.update({"breakdown_value": ["None"]})
                 elif isinstance(breakdown_value, str) or (
                     isinstance(breakdown_value, list) and all(isinstance(item, str) for item in breakdown_value)