Fixes #10173 some more. Mode required was set to hidden.

extension/Classes/Core/Helper/HelperFormElement.php

@@ -715,6 +715,8 @@ EOF;
             case FE_MODE_SHOW_REQUIRED:
                 break;
             case FE_MODE_REQUIRED:
+                $attribute .= Support::doAttribute('required', 'required');
+                break;
             case FE_MODE_READONLY:
 //                $attribute .= Support::doAttribute($feMode, $feMode);
                 $attribute .= Support::doAttribute('disabled', 'disabled');