Undefined index when deleting, if no references are set

I get the following error when deleting, in certain circumstances:

Notice: Undefined index: und in corresponding_node_references_delete() (line 231 of sites/all/modules/cnr/corresponding_node_references.crud.inc).
Warning: Invalid argument supplied for foreach() in corresponding_node_references_delete() (line 231 of sites/all/modules/cnr/corresponding_node_references.crud.inc).

The following patch just checks to make sure that there is actually something to update after a delete.