Fixed Null Ptr Exception in GameState

src/main/java/seng302/gameServer/GameState.java

@@ -1,11 +1,9 @@
 package seng302.gameServer;
 
-import java.util.List;
-import java.util.Map;
-import java.util.Set;
+import java.util.*;
+
 import seng302.models.Player;
 
-import java.util.ArrayList;
 import seng302.models.Yacht;
 import seng302.server.messages.BoatActionType;
 
@@ -32,6 +30,7 @@ public class GameState {
         isRaceStarted = false;
         //set this when game stage changes to prerace
         previousUpdateTime = System.currentTimeMillis();
+        yachts = new HashMap<>();
     }
 
     public static String getHostIpAddress() {