Cache onSelect callback before passing to each dropdown instance

app/assets/javascripts/protected_branch_create.js.es6

@@ -8,38 +8,40 @@
     }
 
     buildDropdowns() {
-      // Allowed to Merge dropdown
       const $allowedToMergeDropdown = this.$wrap.find('.js-allowed-to-merge');
       const $allowedToPushDropdown = this.$wrap.find('.js-allowed-to-push');
 
+      // Cache callback
+      this.onSelectCallback = this.onSelect.bind(this);
+
+      // Allowed to Merge dropdown
       new gl.ProtectedBranchAccessDropdown({
         $dropdown: $allowedToMergeDropdown,
         data: gon.merge_access_levels,
-        onSelect: this.onSelect.bind(this)
+        onSelect: this.onSelectCallback
       });
 
-      // Select default
-      $allowedToMergeDropdown.data('glDropdown').selectRowAtIndex(0);
-
       // Allowed to Push dropdown
       new gl.ProtectedBranchAccessDropdown({
         $dropdown: $allowedToPushDropdown,
         data: gon.push_access_levels,
-        onSelect: this.onSelect.bind(this)
+        onSelect: this.onSelectCallback
       });
 
       // Select default
       $allowedToPushDropdown.data('glDropdown').selectRowAtIndex(0);
+      $allowedToMergeDropdown.data('glDropdown').selectRowAtIndex(0);
 
       // Protected branch dropdown
       new ProtectedBranchDropdown({
         $dropdown: this.$wrap.find('.js-protected-branch-select'),
-        onSelect: this.onSelect.bind(this)
+        onSelect: this.onSelectCallback
       });
     }
 
     // This will run after clicked callback
     onSelect() {
+
       // Enable submit button
       const $branchInput = this.$wrap.find('input[name="protected_branch[name]"]');
       const $allowedToMergeInput = this.$wrap.find('input[name="protected_branch[merge_access_level_attributes][access_level]"]');