Fix form error position when no list is selected

[MAILPOET-2032]

lib/Form/Block/Base.php

@@ -21,6 +21,7 @@ abstract class Base {
       $rules['required'] = true;
       $rules['mincheck'] = 1;
       $rules['group'] = $block['id'];
+      $rules['errors-container'] = '.mailpoet_error_' . $block['id'];
       $rules['required-message'] = WPFunctions::get()->__('Please select a list', 'mailpoet');
     }