when reference is broken, error is hidden

[Schrank]

When the reference in the XML file is broken (e.g. because someone™ is too dumb to know, that you prefix it with the category), the exception thrown is hidden in HTML.

In \Webguys_Easytemplate_Block_Input_Renderer_Reference::getReferenceDefaultName should be checked wether $configModel->getTemplate($this->getReference()) exists and if not and error should be shown