fix spec failures - don't create board config if element doesn't exist

app/assets/javascripts/boards/boards_bundle.js

@@ -191,8 +191,11 @@ $(() => {
     },
   });
 
+  const configEl = document.querySelector('.js-board-config');
+
+  if (configEl) {
     gl.boardConfigToggle = new Vue({
-    el: document.querySelector('.js-board-config'),
+      el: configEl,
       data() {
         return {
           canAdminList: convertPermissionToBoolean(
@@ -220,6 +223,7 @@ $(() => {
         </div>
       `,
     });
+  }
 
   gl.IssueBoardsModalAddBtn = new Vue({
     mixins: [gl.issueBoards.ModalMixins],