fix

DoubleDeckerBus/src/main/java/com/example/doubledeckerbus/DrawingBus.java

@@ -28,6 +28,8 @@ public class DrawingBus {
     }
 
     public void SetPosition(int x, int y, int width, int height) {
+        if (x < 0 || y < 0) return;
+
         if (_pictureWidth <= _busWidth || _pictureHeight <= _busHeight) {
             _pictureWidth = _null;
             _pictureHeight = _null;