small bugfix: suppresses a php notice in sfImageTransformExtraPluginConfiguration (Thanks Christof)
small bugfix: suppresses a php notice in sfImageTransformExtraPluginConfiguration (Thanks Christof)

git-svn-id: e114f0051ae01278a515c06310154043addf1a61@28936 ee427ae8-e902-0410-961c-c3ed070cd9f9

Symfony-Plugins/sfImageTransformExtraPlugin