There is but one goalkeeper
Amend rule “Kicking the Ball” by substituting for the text:
If the result is 2, ownership of the Ball is transferred to a Player of the same position as the target Player, chosen randomly using the GNDT. If the result is 3, the Ball becomes Out of Play and is removed from any Player’s possession.
the text:
If the result is 2 and there exists at least one Player with the same position as the target Player, ownership of the Ball is transferred to such a Player, chosen randomly using the GNDT amongst all Players with that position. Otherwise, the Ball becomes Out of Play and is removed from any Player’s possession.
Such a player may or may not exist.