Catch not filled populateTaxonomy index

In the file gfcptaddon_1-5.php the following code is used;

/*
* Override. Gets the taxonomy from our new field value
*/
function get_field_taxonomy( $field ) {
      return $field['populateTaxonomy'];
}

When field is not filled, ergo not set, this results in warnings. Should be cleaner to add a if-statement around it, to catch that. Something like this:

/*
* Override. Gets the taxonomy from our new field value
*/
function get_field_taxonomy( $field ) {
        if(isSet($field['populateTaxonomy']))
        {
            	return $field['populateTaxonomy'];
        }

        return null;
}