Fixed a bug that game client tries to send turning mode packet when there is no socketThread

- add a if statement to check if socketThread is initialized before sending packet.

#story[1278]

src/main/java/seng302/visualiser/GameClient.java

@@ -461,6 +461,7 @@ public class GameClient {
     }
 
     public void sendToggleTurningModePacket() {
+        if (socketThread != null) {
             if (gameKeyBind.isContinuouslyTurning()) {
                 socketThread.sendBoatAction(BoatAction.CONTINUOUSLY_TURNING);
             } else {
@@ -468,3 +469,4 @@ public class GameClient {
             }
         }
     }
+}