Fix payload driver crash (#5565)

Similar to the mass driver one, https://i-dont.go-outsi.de/53ZwBY_YS.png

core/src/mindustry/world/blocks/payloads/PayloadMassDriver.java

@@ -456,6 +456,7 @@ public class PayloadMassDriver extends PayloadBlock{
 
         @Override
         public Point2 config(){
+            if(tile == null) return null;
             return Point2.unpack(link).sub(tile.x, tile.y);
         }