Guardian: fix Brace causing a softlock when the player doesn't have Mode Shift

[modargo]

This bug was reported by someone playing Spire Biomes because there are various ways to get cards from other characters. Bracing when the player didn't have ModeShiftPower would softlock because BraceAction queued an action that never set isDone.

This PR implements a fix, which is very simple. I tested it locally.