Fix display the form errors correctly

Use `property_path` form option to map underscored form fields
to object properties

@see https://github.com/symfony/symfony/issues/9162#issuecomment-25431148

Fix #3067

src/Wallabag/ApiBundle/Form/Type/ClientType.php

@@ -16,7 +16,11 @@ class ClientType extends AbstractType
     {
         $builder
             ->add('name', TextType::class, ['label' => 'developer.client.form.name_label'])
-            ->add('redirect_uris', UrlType::class, ['required' => false, 'label' => 'developer.client.form.redirect_uris_label'])
+            ->add('redirect_uris', UrlType::class, [
+                'required' => false,
+                'label' => 'developer.client.form.redirect_uris_label',
+                'property_path' => 'redirectUris',
+            ])
             ->add('save', SubmitType::class, ['label' => 'developer.client.form.save_label'])
         ;