fix ai NPE when selecting a unit where to spawn frost pylon

The NPE is caused by any piled permanent with which TilesInRange is
called.

1 files changed, 3 insertions, 12 deletions

diff --git a/go/game/unit.go b/go/game/unit.go
index adb608ab..c6c1839a 100644
--- a/go/game/unit.go
+++ b/go/game/unit.go
@@ -63,11 +63,11 @@ func NewUnit(card *Card, tile *Tile, owner *Player) *Unit {
 }
 
 func (u *Unit) Fmt() string {
-	return fmt.Sprintf("%s@%v", u.Card().Name, u.TileOrContainingPermTile())
+	return fmt.Sprintf("%s@%v", u.Card().Name, TileOrContainingPermTile(u))
 }
 
 func (u *Unit) FmtWController() string {
-	return fmt.Sprintf("%s's %s@%v", u.Controller().Name, u.Card().Name, u.TileOrContainingPermTile())
+	return fmt.Sprintf("%s's %s@%v", u.Controller().Name, u.Card().Name, TileOrContainingPermTile(u))
 }
 
 func NewUnitFromPath(cardPath string, tile *Tile, owner *Player) *Unit {
@@ -107,20 +107,11 @@ func (u *Unit) move(s *State, tile *Tile) {
 	}
 }
 
-func (u *Unit) TileOrContainingPermTile() *Tile {
-	tile := u.tile
-	if tile == nil {
-		tile = u.containingPerm.Tile()
-	}
-
-	return tile
-}
-
 func (u *Unit) MoveRangeTiles(m *Map) []*Tile {
 	tiles := []*Tile{}
 	// TODO: build graph only containing possible tile in movement range
 	graph := m.generateMapGraphFor(u)
-	origin := u.TileOrContainingPermTile().Position
+	origin := TileOrContainingPermTile(u).Position
 	for _, pos := range PositionsInRange(origin, u.Movement.Range, false) {
 		tile := m.TileAt(pos)
 		if tile == nil || !u.IsAvailableTile(tile) {