Fix configuration

DependencyInjection/Configuration.php

@@ -40,8 +40,14 @@ class Configuration implements ConfigurationInterface
                 ->arrayNode('templates')
                     ->addDefaultsIfNotSet()
                     ->children()
-                        ->scalarNode('form')->defaultValue(array('SonataDoctrineORMAdminBundle:Form:form_admin_fields.html.twig'))->cannotBeEmpty()->end()
-                        ->scalarNode('filter')->defaultValue(array('SonataDoctrineORMAdminBundle:Form:filter_admin_fields.html.twig'))->cannotBeEmpty()->end()
+                        ->arrayNode('form')
+                            ->prototype('scalar')->end()
+                            ->defaultValue(array('SonataDoctrineORMAdminBundle:Form:form_admin_fields.html.twig'))
+                        ->end()
+                        ->arrayNode('filter')
+                            ->prototype('scalar')->end()
+                            ->defaultValue(array('SonataDoctrineORMAdminBundle:Form:filter_admin_fields.html.twig'))
+                        ->end()
                     ->end()
                 ->end()
             ->end()