[Gameplay] Mordekaiser Ult Icon Bug

Occasionally, when Mordekaiser's grave-child ghost dies, the ult icon will not grey out or show the cooldown timer. Instead, it will light up, giving the illusion that your ult is off cooldown. A few times now I've been screwed in team-fights and skirmishes where I'm spamming r and nothing happens. The glitch has occurred in two different games, and always near the end of the game. I have yet to see the glitch occur when a dragon ghost dies.