fixed breadcrumbs being undefined

app/assets/javascripts/breadcrumb.js

@@ -8,6 +8,8 @@ export const addTooltipToEl = (el) => {
 
 export default () => {
   const breadcrumbs = document.querySelector('.breadcrumbs-list');
+
+  if (breadcrumbs) {
     const topLevelLinks = breadcrumbs.querySelectorAll('.breadcrumbs-list > li > a');
     const $expander = $('.js-breadcrumbs-collapsed-expander');
 
@@ -18,4 +20,5 @@ export default () => {
         $('.js-breadcrumbs-collapsed-expander', e.currentTarget).toggleClass('open')
           .tooltip('hide');
       });
+  }
 };