entity_type hook always displays operation as "Array"

The userpoints entity_type hook operation doesn't work as expected in the current 6.x-1.x-dev version.

$operation = module_invoke_all('userpoints', 'entity_type', $data);

module_invoke_all() always returns an array, but the code after this expects $operation to be a string. Implementing this hook in a module means that the operation column is displayed as "Array" instead of the string (or link) that is returned. The attached patch fixes this by using the first element of the array as the operation string if one is returned.