fix load_nids to filter rows with two elements

[PliskinDev]

modified load_nids to filter rows with exactly two elements.
prevents ValueError during CSV processing, improving stability and correctness of NID loading.

[SocraticBliss]

While I completely agree that loading in an invalid file could (should?) be handled better, if we were to go to this level of checking, we should probably let the user know that the file that they have provided is invalid due to them adding another column.

Regardless, the principle is sound, I will add some additional logic there and give you the proper credit :)

Then I'll close out this when it is implemented.

Thanks again for submission!