fix: clouse issue #2469 by fixing the type (#2533)

Signed-off-by: yihong0618 <zouzou0208@gmail.com>

packages/dbgpt-app/src/dbgpt_app/scene/chat_db/professional_qa/chat.py

@@ -38,9 +38,7 @@ class ChatWithDbQA(BaseChat):
         if self.database.is_graph_type():
             # When the current graph database retrieves source data from ChatDB, the
             # topk uses the sum of node table and edge table.
-            self.top_k = len(self.tables["vertex_tables"]) + len(
-                self.tables["edge_tables"]
-            )
+            self.top_k = len(list(self.tables))
         else:
             logger.info(f"Dialect: {self.database.db_type}")
             self.top_k = self.curr_config.schema_retrieve_top_k