修复handler为空时导致的bug

Author: binarywang

weixin-java-mp/src/main/java/me/chanjar/weixin/mp/api/WxMpMessageRouterRule.java

@@ -211,6 +211,9 @@ protected WxMpXmlOutMessage service(WxMpXmlMessage wxMessage,
       WxMpXmlOutMessage res = null;
       for (WxMpMessageHandler handler : this.handlers) {
         // 返回最后handler的结果
+        if(handler == null){
+          continue;
+        }
         res = handler.handle(wxMessage, context, wxMpService, sessionManager);
       }
       return res;