Thieves' Auction soft-locks with MDFCs

[[Thieves' Auction]] doesn't let any player choose a MDFC it exiled, causing the game to become soft-locked.
The issue occurs regardless of which face of the MDFC was up when it got exiled. For example, both [[Tergrid, God of Fright]] and [[Venom, Lethal Protector]] encounter this issue.

Reproduce the soft-lock with Thieves' Auction using Tergrid, God of Fright and Venom, Lethal Protector, testing both faces when exiled. Start by tracing the auction's card-selection handling for MDFCs. Done means every player can choose an exiled MDFC and the auction completes regardless of which face was up.

Written by the indexing model from the issue text.