It would be an indirect free kick had Dawson played the ball or challenged an opponent, as per this from law 12 ...
Advantage should not be applied in situations involving serious foul play, violent conduct or a second cautionable offence unless there is a clear opportunity to score a goal. The referee must send off the player when the ball is next out of play, but if the player plays the ball or challenges/interferes with an opponent, the referee will stop play, send off the player and restart with an indirect free kick, unless the player committed a more serious offence.