wip,chat: forking edits

backend/src/server/websocket.py

@@ -285,7 +285,7 @@ def register(server, app, auth_manager):
                 elif action == "fork-chat-thread":
                     thread_id = await app.fork_chat_thread(
                         thread_id=body['threadId'],
-                        message_id=body['messageId'],
+                        message_id=body.get('messageId'),
                     )
                     await send({'message': "chat thread created", 'threadId': thread_id, 'nonce': nonce})