Issue #3314089 by immaculatexavier: Undefined index views_send in views_form_validate

views/views_send_handler_field_selector.inc

@@ -51,7 +51,7 @@ class views_send_handler_field_selector extends views_handler_field {
 
   function views_form_validate($form, &$form_state) {
     $field_name = $this->options['id'];
-    $selection = array_filter($form_state['values'][$field_name]);
+    $selection = array_filter($form_state['values'][$field_name] ?: []);
 
     if (empty($selection)) {
       form_set_error($field_name, t('Please select at least one item.'));