Remove `undefined` class from `.emoji-menu-list`

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/30496

app/assets/javascripts/awards_handler.js

@@ -51,7 +51,7 @@ function renderCategory(name, emojiList, opts = {}) {
     <h5 class="emoji-menu-title">
       ${name}
     </h5>
-    <ul class="clearfix emoji-menu-list ${opts.menuListClass}">
+    <ul class="clearfix emoji-menu-list ${opts.menuListClass || ''}">
       ${emojiList.map(emojiName => `
         <li class="emoji-menu-list-item">
           <button class="emoji-menu-btn text-center js-emoji-btn" type="button">