增加判断是否有人工客服帐号，避免出现无账号时候，头像为默认头像的情况 (#502)

* Update MessageBuilder.php

增加判断是否有人工客服帐号，避免出现无账号时候，头像为默认头像的情况

* Update MessageBuilder.php

样式fix

* 增加判断是否有人工客服帐号，避免出现无账号时候，头像为默认头像的情况

src/Staff/MessageBuilder.php

@@ -136,11 +136,15 @@ public function send()
             $message = $this->message->get('content');
         } else {
             $content = $transformer->transform($this->message);
-
-            $message = array_merge([
+            $message = [
                 'touser' => $this->to,
-                'customservice' => ['kf_account' => $this->account],
-            ], $content);
+            ];
+
+            if ($this->account) {
+                $message['customservice'] = ['kf_account' => $this->account];
+            }
+
+            $message = array_merge($message, $content);
         }
 
         return $this->staff->send($message);