EntityResourceReferenceHandler are not called anymore

Since the changes performed to get rid of struts in 13.0 we apparently lost the capability to execute an EntityResourceReferenceHandler.
It uses to be possible through a fallback on XWikiAction with an UnknownAction and then a call to the EntityResourceReferenceHandler. Now there's a check if the action exist, which prevents this call to the EntityResourceReferenceHandler.