Update preMount validation data code

Author: cavasinf

src/TwigComponent/doc/index.rst

@@ -468,12 +468,14 @@ component use a ``PreMount`` hook::
         {
             // validate data
             $resolver = new OptionsResolver();
+            $resolver->setIgnoreUndefined(true);
+
             $resolver->setDefaults(['type' => 'success']);
             $resolver->setAllowedValues('type', ['success', 'danger']);
             $resolver->setRequired('message');
             $resolver->setAllowedTypes('message', 'string');
 
-            return $resolver->resolve($data);
+            return $resolver->resolve($data) + $data;
         }
 
         // ...