Issue #3396553: Error when adding rate widget to a view and unable to edit field

Closes #3396553

src/Plugin/views/field/RateWidgetField.php

@@ -46,7 +46,7 @@ class RateWidgetField extends FieldPluginBase {
     $field_list = [];
     $field_handlers = $this->view->getHandlers('field');
     foreach ($field_handlers as $field_name) {
-      if ($field_name['entity_type'] && $field_name['plugin_id'] != 'rate_widget_field') {
+      if (isset($field_name['entity_type']) && $field_name['plugin_id'] != 'rate_widget_field') {
         if (empty($field_name['label'])) {
           $field_list[$field_name['id']] = $field_name['id'];
         }