Hive: close connection only if it exists

redash/query_runner/hive_ds.py

@@ -124,7 +124,8 @@ class Hive(BaseSQLQueryRunner):
             logging.exception(e)
             raise sys.exc_info()[1], None, sys.exc_info()[2]
         finally:
-            connection.close()
+            if connection:
+                connection.close()
 
         return json_data, error