Relation incorrectly assumes that all entity types have a entitytype_view() function

Used ECK to create a new entity type called 'model.'
Created relation type where a model bundle is one of the endpoints.
Edited a relation and hit save to get to the 'view' page of the relation, got an error about function model_view() not being found in relation_endpoint_field_formatter_view(), on line 277 of relation_endpoint.module.

Relation should run the function name through function_exists() before trying to call it.

In my case I have the Entity module installed, so I was able to put together a simple work around:

function model_view($entity, $view_mode) {
  return entity_view('model', array($entity->id => $entity), $view_mode);
}

entity_view() is part of the Entity module.