Fixed issue win ResizableRaceCanvas

- Issue where the boat position may mess up if it is called before the server has sent us information about hte location.
#story[782]

visualiser/src/main/java/seng302/Model/ResizableRaceCanvas.java

@@ -84,6 +84,7 @@ public class ResizableRaceCanvas extends Canvas {
     }
 
     public void displayBoat(Boat boat, double angle, Color colour) {
+        if (boat.getCurrentPosition() != null) {
             GraphCoordinate pos = this.map.convertGPS(boat.getCurrentPosition());
             Paint paint = colour;
 
@@ -96,6 +97,7 @@ public class ResizableRaceCanvas extends Canvas {
             gc.fillPolygon(x, y, 3);
             gc.restore();
         }
+    }
 
     /**
      * Displays a line on the map with rectangles on the starting and ending point of the line.