Fix Advanced Search retry migration button

Changelog: fixed
EE: true

ee/app/views/admin/application_settings/_elasticsearch_form.html.haml

@@ -31,7 +31,7 @@
                   = link_to _('Learn more.'), help_page_path('integration/elasticsearch', anchor: 'advanced-search-migrations')
                 .gl-alert-actions
                   - migration = Elastic::DataMigrationService.halted_migration
-                  = link_to _('Retry migration'), admin_elasticsearch_retry_migration_path(version: migration.version), class: 'btn gl-alert-action btn-warning gl-button', disabled: @elasticsearch_reindexing_task&.in_progress?, data: { confirm: _('Are you sure you want to retry this migration?') }, method: :post
+                  = link_to _('Retry migration'), admin_elasticsearch_retry_migration_path(version: migration.version), class: 'btn gl-alert-action btn-warning gl-button', disabled: @last_elasticsearch_reindexing_task&.in_progress?, data: { confirm: _('Are you sure you want to retry this migration?') }, method: :post
 
             .form-group
               .form-check

ee/spec/views/admin/application_settings/_elasticsearch_form.html.haml_spec.rb

@@ -228,11 +228,27 @@ RSpec.describe 'admin/application_settings/_elasticsearch_form' do
         allow(Elastic::DataMigrationService).to receive(:halted_migration).and_return(migration)
       end
 
-      it 'shows the retry migration card' do
-        render
+      context 'when there is no reindexing' do
+        it 'shows the retry migration card' do
+          render
+
+          expect(rendered).to include('There is a halted Elasticsearch migration')
+          expect(rendered).to have_css('a', text: 'Retry migration')
+          expect(rendered).not_to have_css('a[disabled="disabled"]', text: 'Retry migration')
+        end
+      end
 
-        expect(rendered).to include('There is a halted Elasticsearch migration')
-        expect(rendered).to include('Retry migration')
+      context 'when there is a reindexing task in progress' do
+        before do
+          assign(:last_elasticsearch_reindexing_task, build(:elastic_reindexing_task))
+        end
+
+        it 'shows the retry migration card with retry button disabled' do
+          render
+
+          expect(rendered).to include('There is a halted Elasticsearch migration')
+          expect(rendered).to have_css('a[disabled="disabled"]', text: 'Retry migration')
+        end
       end
     end