fix: chart import (#25425)

superset/charts/commands/importers/v1/utils.py

@@ -99,8 +99,8 @@ def migrate_chart(config: dict[str, Any]) -> dict[str, Any]:
 
     # also update `query_context`
     try:
-        query_context = json.loads(output.get("query_context", "{}"))
-    except json.decoder.JSONDecodeError:
+        query_context = json.loads(output.get("query_context") or "{}")
+    except (json.decoder.JSONDecodeError, TypeError):
         query_context = {}
     if "form_data" in query_context:
         query_context["form_data"] = output["params"]

tests/unit_tests/charts/commands/importers/v1/utils_test.py

@@ -32,6 +32,7 @@ def test_migrate_chart_area() -> None:
         "certified_by": None,
         "certification_details": None,
         "viz_type": "area",
+        "query_context": None,
         "params": json.dumps(
             {
                 "adhoc_filters": [],