Improve code style

Refer to: cocos2d/cocos2d-x#20743

Author: halx99

core/ui/UIRichText.cpp

@@ -689,7 +689,7 @@ void MyXMLVisitor::startElement(void* /*ctx*/, const char* elementName, const ch
             auto result                = tagBehavior.handleVisitEnter(tagAttrValueMap);
             ValueMap& attrValueMap     = result.first;
             RichElement* richElement   = result.second;
-            if (!attrValueMap.empty())
+            if (tagBehavior.isFontElement)
             {
                 Attributes attributes;