Set listener loggers to fos_elastica.logger if null

DependencyInjection/Configuration.php

@@ -290,6 +290,7 @@ class Configuration implements ConfigurationInterface
                                     ->scalarNode('delete')->defaultTrue()->end()
                                     ->booleanNode('immediate')->defaultFalse()->end()
                                     ->scalarNode('logger')
+                                        ->treatNullLike('fos_elastica.logger')
                                         ->treatTrueLike('fos_elastica.logger')
                                     ->end()
                                     ->scalarNode('service')->end()

Persister/ObjectPersister.php

@@ -180,4 +180,4 @@ class ObjectPersister implements ObjectPersisterInterface
     {
         return $this->transformer->transform($object, $this->fields);
     }
-}
+}