fix(#999): add tips for tag no description

ui/src/i18n/locales/en.json

@@ -332,6 +332,7 @@
     "button_following": "Following",
     "tag_label": "questions",
     "search_placeholder": "Filter by tag name",
+    "no_description": "The tag has no description",
     "more": "More"
   },
   "ask": {

ui/src/pages/Tags/Detail/index.tsx

@@ -70,7 +70,7 @@ const Questions: FC = () => {
               </h3>
 
               <p className="text-break">
-                {tagInfo.excerpt}
+                {tagInfo.excerpt || t('no_description')}
                 <Link to={`/tags/${curTagName}/info`}> [{t('more')}]</Link>
               </p>