Prevent iterate with empty method annotations

This avoid ErrorException raised when a empty annotation gets reach the foreach. This class has a lot foreach without prevent checking empty values. It should be improved in a future.

	ErrorException: Warning: Invalid argument supplied for foreach() in /var/www/dev/vendor/jms/di-extra-bundle/JMS/DiExtraBundle/Metadata/Driver/AnnotationDriver.php line 141
	at ErrorHandler->handle('2', 'Invalid argument supplied for foreach()', '/var/www/dev/vendor/jms/di-extra-bundle/JMS/DiExtraBundle/Metadata/Driver/AnnotationDriver.php', '141', array('class' => object(ReflectionClass), 'metadata' => object(ClassMetadata), 'className' => 'MyClass', 'filename' => 'MyFile', 'hasInjection' => false, 'property' => object(ReflectionProperty), 'name' => 'myAction', 'method' => object(ReflectionMethod))) in /var/www/dev/vendor/jms/di-extra-bundle/JMS/DiExtraBundle/Metadata/Driver/AnnotationDriver.php line 141
	at AnnotationDriver->loadMetadataForClass(object(ReflectionClass)) in /var/www/dev/vendor/jms/metadata/src/Metadata/Driver/LazyLoadingDriver.php line 20
	at LazyLoadingDriver->loadMetadataForClass(object(ReflectionClass)) in /var/www/dev/vendor/jms/metadata/src/Metadata/MetadataFactory.php line 77
	at MetadataFactory->getMetadataForClass('MyClassr') in /var/www/dev/vendor/jms/di-extra-bundle/JMS/DiExtraBundle/HttpKernel/ControllerResolver.php line 84