malformed node reference structure due to missing field language during node import

Problem/Motivation

After importing node references, a node id is displayed in the imported field, but the node is not referenced. During the import process, the referenced nid is assigned to the incorrect part of the $node structure.

    [field_featured_questions] => Array
        (
            [und] => Array
                (
                    [0] => Array
                        (
                            [nid] => 3362
                        )

                )

            [0] => Array
                (
                    [nid] => 3696
                )

        )

It should look like this:

    [field_featured_questions] => Array
        (
            [und] => Array
                (
                    [0] => Array
                        (
                            [nid] => 3362
                        )

                )

        )

Proposed resolution

Apply the attached patch or re-reference the node id manually through the node edit interface.

Remaining tasks

Please review the patch. I opted to use the field API instead of $node->language, since the node reference field may have multiple languages. Because multiple languages for a node reference may be rare, I left complete support for multiple languages for a later date.