Merge pull request #2 from Nicofuma/patch-1

Null isn't a valid value for prefetchSize

Author: ooflorent

DependencyInjection/Configuration.php

@@ -73,7 +73,7 @@ public function getConfigTreeBuilder()
                                 ->children()
                                     ->scalarNode('type')->defaultValue('queue')->end()
                                     ->scalarNode('name')->isRequired()->end()
-                                    ->scalarNode('prefetchSize')->defaultNull()->end()
+                                    ->scalarNode('prefetchSize')->defaultValue(1)->end()
                                 ->end()
                             ->end()
                         ->end()