fixed JS issue when description doesnt exist on the page

app/assets/javascripts/issue_show/index.js

@@ -5,7 +5,7 @@ import '../vue_shared/vue_resource_interceptor';
 (() => {
   const issueTitleData = document.querySelector('.issue-title-data').dataset;
   const initialTitle = document.querySelector('.js-issue-title').innerHTML;
-  const initialDescription = document.querySelector('.js-issue-description').innerHTML;
+  const initialDescription = document.querySelector('.js-issue-description');
   const { canUpdateTasksClass, endpoint, isEdited } = issueTitleData;
   const vm = new Vue({
@@ -16,7 +16,7 @@ import '../vue_shared/vue_resource_interceptor';
         endpoint,
         isEdited,
         initialTitle,
-        initialDescription,
+        initialDescription: initialDescription ? initialDescription.innerHTML : '',
       },
     }),
   });