Fix Map.Contains checks for maps with height.

If a cell lacked any valid projected cells, then it is off the map entirely. The previous logic would think such a cell was within the map as none of projected cells were out of bounds (as there were no projected cells to fail the check).

OpenRA.Game/Map/Map.cs

@@ -771,7 +771,12 @@ namespace OpenRA
 			if (Grid.MaximumTerrainHeight == 0)
 				return Contains((PPos)uv);
 
-			foreach (var puv in ProjectedCellsCovering(uv))
+			// If the cell has no valid projection, then we're off the map.
+			var projectedCells = ProjectedCellsCovering(uv);
+			if (projectedCells.Length == 0)
+				return false;
+
+			foreach (var puv in projectedCells)
 				if (!Contains(puv))
 					return false;
 			return true;