修复 解决在低版本的 nodejs 环境下不支持可先链的问题

uniCloud/cloudfunctions/uni-im-co/msg.js

@@ -460,7 +460,7 @@ async function _createOrUpdateConversation(conversation_id, msgData, chat_source
                     })
                     .get()
         // console.error('createOrUpdateConversation receiver~~~~~', receiver);
-        if(receiver && receiver.role?.includes('staff')){
+        if(receiver && receiver.role && receiver.role.includes('staff')){
           // console.error('createOrUpdateConversation receiver.staff~~~~~');
           check = true
         }