Fix: fix mismatch of assitant message and its reference (#9233)

### What problem does this PR solve?

#9232

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

1. When creating a new session, initialize an empty reference that
includes both the app api and sdk API.
2. Fix the logic when retrieving references for historical messages: the
number of dialogue messages and reference messages may differ, but it
should match the number of assistant messages.

Co-authored-by: Li Ye <liye@unittec.com>

api/apps/conversation_app.py

@@ -66,7 +66,8 @@ def set_conversation():
         e, dia = DialogService.get_by_id(req["dialog_id"])
         if not e:
             return get_data_error_result(message="Dialog not found")
-        conv = {"id": conv_id, "dialog_id": req["dialog_id"], "name": name, "message": [{"role": "assistant", "content": dia.prompt_config["prologue"]}],"user_id": current_user.id}
+        conv = {"id": conv_id, "dialog_id": req["dialog_id"], "name": name, "message": [{"role": "assistant", "content": dia.prompt_config["prologue"]}],"user_id": current_user.id,
+                "reference":[{}],}
         ConversationService.save(**conv)
         return get_json_result(data=conv)
     except Exception as e: