Issue #1824180 by fubhy: Fixed Undefined variable () in Field UI module.

core/modules/field/tests/modules/field_test/field_test.module

@@ -279,3 +279,11 @@ function field_test_field_formatter_settings_form_alter(&$element, &$form_state,
 function field_test_field_formatter_settings_summary_alter(&$summary, $context) {
   $summary .= '<br />field_test_field_formatter_settings_summary_alter';
 }
+
+/**
+ * Implements hook_field_extra_fields_alter().
+ */
+function field_test_field_extra_fields_alter(&$info) {
+  // Remove all extra fields from the 'no_fields' content type;
+  unset($info['node']['no_fields']);
+}

core/modules/field_ui/lib/Drupal/field_ui/DisplayOverview.php

@@ -63,7 +63,7 @@ public function form(array $form, array &$form_state) {
     );
 
     if (empty($instances) && empty($extra_fields)) {
-      drupal_set_message(t('There are no fields yet added. You can add new fields on the <a href="@link">Manage fields</a> page.', array('@link' => url($admin_path . '/fields'))), 'warning');
+      drupal_set_message(t('There are no fields yet added. You can add new fields on the <a href="@link">Manage fields</a> page.', array('@link' => url($this->adminPath . '/fields'))), 'warning');
       return $form;
     }
 

core/modules/field_ui/lib/Drupal/field_ui/Tests/ManageDisplayTest.php

@@ -178,6 +178,20 @@ function testSingleViewMode() {
     $this->drupalPost('admin/config/people/accounts/display', array(), t('Save'));
   }
 
+  /**
+   * Tests that a message is shown when there are no fields.
+   */
+  function testNoFieldsDisplayOverview() {
+    // Create a fresh content type without any fields.
+    $this->drupalCreateContentType(array('type' => 'no_fields', 'name' => 'No fields'));
+
+    // Remove the 'body' field.
+    field_delete_instance(field_info_instance('node', 'body', 'no_fields'));
+
+    $this->drupalGet('admin/structure/types/manage/no_fields/display');
+    $this->assertRaw(t('There are no fields yet added. You can add new fields on the <a href="@link">Manage fields</a> page.', array('@link' => url('admin/structure/types/manage/no_fields/fields'))));
+  }
+
   /**
    * Asserts that a string is found in the rendered node in a view mode.
    *