v1.1 rule: If no black overfatigue dice remain in the supply, adventurers must take 1 true damage for each overfatigue they are unable to place in their cooldown track.
v1.0 rule: If no black overfatigue dice remain in the supply, no fatigue dice are placed.
Adjusted on page 21 of the rulebook.
(Note: that these adjustments are not yet made to printed items or digital files. They will be rolled out officially during the release of the Heroes of Tamriel campaign.)