Error message during import of contacts

During a Contact import I get this error

Notice: Undefined index: 4_a_b in CRM_Import_Parser_Contact->checkRelatedContactFields() (line 1973 of /var/www/jenkins/live_jenkins-tfglive-5/sites/all/modules/contrib/civicrm/CRM/Import/Parser/Contact.php).

The import is in this example a testtfg.csv file.
First Name, Last Name, Email and Org Name

The Options are skip or update for matching (I tried both)
The De-dupe rule is Fuzzy

The import still works.

This is not an issue on Demo site.

I altered the file Contact.php line
1973 to be

if ( array_key_exists($name, $relatedContactFields) ) {

instead of
if ( !is_array( $relatedContactFields[$name] ) ) {

And the issue goes away but I am not sure what other issues I caused by doing that.

Attached are the screenshots of the import process and errors and the file for testing.