fix: restore missing arguments to getGroundHeight call

Author: bobtista

Generals/Code/GameEngine/Source/GameLogic/Map/TerrainLogic.cpp

@@ -2710,7 +2710,7 @@ void TerrainLogic::flattenTerrain(Object *obj)
 
 			// Compare to the height at the building's origin, because setRawMapHeight will only lower,
 			// not raise.  jba
-			Int centerHeight = REAL_TO_INT_FLOOR(getGroundHeight()/MAP_HEIGHT_SCALE);
+			Int centerHeight = REAL_TO_INT_FLOOR(getGroundHeight(pos->x, pos->y)/MAP_HEIGHT_SCALE);
 			if (rawDataHeight>centerHeight) rawDataHeight = centerHeight;
 
 			for (i=iMin.x; i<=iMax.x; i++) {