return default parameter value of ZDungeonLevel::TryToMoveMonster
to actually compile tests
add nullptr-check to PlaceMonster in both ZDungeonLevel and ZDungeon
remove duplicate checks from ZDungeon::PlaceMonster
cause it calls ZDungeonLevel::PlaceMonster which already has such checks
simplify some tests for ZDungeonLevel::GetMonster
cause method now takes monster as pointer instead of value
fix typo in test for ZDungeonLevel::GetMonster