Improve projects/groups list js code

app/assets/javascripts/filterable_list.js

@@ -7,8 +7,6 @@ export default class FilterableList {
     this.filterForm = form;
     this.listFilterElement = filter;
     this.listHolderElement = holder;
-
-    this.initSearch();
   }
 
   initSearch() {

app/assets/javascripts/groups_list.js

@@ -6,10 +6,13 @@ import FilterableList from './filterable_list';
  */
 export default class GroupsList {
   constructor() {
-    var form = document.querySelector('form#group-filter-form');
-    var filter = document.querySelector('.js-groups-list-filter');
-    var holder = document.querySelector('.js-groups-list-holder');
+    const form = document.querySelector('form#group-filter-form');
+    const filter = document.querySelector('.js-groups-list-filter');
+    const holder = document.querySelector('.js-groups-list-holder');
 
-    new FilterableList(form, filter, holder);
+    if (form && filter && holder) {
+      const list = new FilterableList(form, filter, holder);
+      list.initSearch();
+    }
   }
 }

app/assets/javascripts/projects_list.js

@@ -6,10 +6,13 @@ import FilterableList from './filterable_list';
  */
 export default class ProjectsList {
   constructor() {
-    var form = document.querySelector('form#project-filter-form');
-    var filter = document.querySelector('.js-projects-list-filter');
-    var holder = document.querySelector('.js-projects-list-holder');
+    const form = document.querySelector('form#project-filter-form');
+    const filter = document.querySelector('.js-projects-list-filter');
+    const holder = document.querySelector('.js-projects-list-holder');
 
-    new FilterableList(form, filter, holder);
+    if (form && filter && holder) {
+      const list = new FilterableList(form, filter, holder);
+      list.initSearch();
+    }
   }
 }