Fixed momentary "flash" when removing respawn protection from player with invulnerability sphere
A small oversight of 008b17e6477f: removing APowerRespawnInvulnerable
from a player also removes any active colourmap on them. So, if they already have another invulnerability powerup (e.g. invulnerability sphere), the colourmap will momentarily disappear, then re-appear, creating an undesirable "flash" effect".