Prevent NPE if trying to restore an already restored deleted branch (#21940)

If a deleted-branch has already been restored, a request to restore it
again will cause a NPE. This PR adds detection for this case, but also
disables buttons when they're clicked in order to help prevent
accidental repeat requests.

Fix #21930

Signed-off-by: Andrew Thornton <art27@cantab.net>

web_src/js/features/common-global.js

@@ -260,6 +260,7 @@ export function initGlobalLinkActions() {
     e.preventDefault();
     const $this = $(this);
     const redirect = $this.data('redirect');
+    $this.prop('disabled', true);
     $.post($this.data('url'), {
       _csrf: csrfToken
     }).done((data) => {
@@ -270,6 +271,8 @@ export function initGlobalLinkActions() {
       } else {
         window.location.reload();
       }
+    }).always(() => {
+      $this.prop('disabled', false);
     });
   }
 
@@ -283,11 +286,14 @@ export function initGlobalLinkActions() {
   // FIXME: this is only used once, and should be replace with `link-action` instead
   $('.undo-button').on('click', function () {
     const $this = $(this);
+    $this.prop('disabled', true);
     $.post($this.data('url'), {
       _csrf: csrfToken,
       id: $this.data('id')
     }).done((data) => {
       window.location.href = data.redirect;
+    }).always(() => {
+      $this.prop('disabled', false);
     });
   });
 }