fix(ingest/trino): Avoid exception if $properties table empty or not …

…readable (datahub-project#5447)

Under some configuration of access rules in Trino, the user may not have
read access to the content of the table, which will result in an exception
(`fetchone()` returns `None`)

This commit ensures no exception are raised and the ingestion can proceed.

metadata-ingestion/src/datahub/ingestion/source/sql/trino.py

@@ -71,8 +71,9 @@ def get_table_comment(self, connection, table_name: str, schema: str = None, **k
 
         # Generate properties dictionary.
         properties = {}
-        for col_name, col_value in row.items():
-            properties[col_name] = col_value
+        if row:
+            for col_name, col_value in row.items():
+                properties[col_name] = col_value
 
         return {"text": properties.get("comment", None), "properties": properties}
     except TrinoQueryError as e: