Check if the baord is completed and return to main menu

app/src/main/java/school_project/Piece.java

@@ -42,6 +42,8 @@ public class Piece extends Shape{
 
     public ArrayList<Vec2> getOccupation(){
         ArrayList<Vec2> ret = new ArrayList<>();
+        if(Position == null)
+            return ret;
         for (int x = 0; x < height; x++) {
             for (int y = 0; y < width; y++) {
                if(getShape()[x][y]){