KeeperRL v1.0 hotfix 4 is out

All undead get the swimming skill.
Fixed a crash when a summoned spirit is killed and in the same turn the team returns to base.
Fixed a crash in the creature choice menu when using keys.
Fixed a crash in the polymorph spell.
Fixed a UI crash.
Fixed a crash in retiring a villain.
Fixed a modded spell crash.
Improved crash reporting in cases when dungeon retirement fails.