Moved the duplicate Available Refs to a default in RefSelectDropdown

app/assets/javascripts/dispatcher.js

@@ -251,7 +251,7 @@ import PerformanceBar from './performance_bar';
         case 'projects:tags:new':
           new ZenMode();
           new gl.GLForm($('.tag-form'), true);
-          new RefSelectDropdown($('.js-branch-select'), JSON.parse(document.getElementById('availableRefs').innerHTML));
+          new RefSelectDropdown($('.js-branch-select'));
           break;
         case 'projects:snippets:new':
         case 'projects:snippets:edit':
@@ -318,7 +318,7 @@ import PerformanceBar from './performance_bar';
           setupProjectEdit();
           break;
         case 'projects:pipelines:new':
-          new NewBranchForm($('.js-new-pipeline-form'), JSON.parse(document.getElementById('availableRefs').innerHTML));
+          new NewBranchForm($('.js-new-pipeline-form'));
           break;
         case 'projects:pipelines:builds':
         case 'projects:pipelines:failures':

app/assets/javascripts/ref_select_dropdown.js

 class RefSelectDropdown {
   constructor($dropdownButton, availableRefs) {
+    const availableRefsValue = availableRefs || JSON.parse(document.getElementById('availableRefs').innerHTML);
     $dropdownButton.glDropdown({
-      data: availableRefs,
+      data: availableRefsValue,
       filterable: true,
       filterByText: true,
       remote: false,