add no-args constructor to state classes to satisfy Kryo requirement

core/src/no/ntnu/trostespel/PlayerActions.java

@@ -25,6 +25,5 @@ public PlayerActions(int pid) {
     }
 
     public PlayerActions() {
-        pid = new Random().nextInt();
     }
 }

core/src/no/ntnu/trostespel/state/MovableState.java

@@ -1,6 +1,7 @@
 package no.ntnu.trostespel.state;
 
 import com.badlogic.gdx.math.Vector2;
+import no.ntnu.trostespel.entity.Movable;
 
 import java.util.concurrent.atomic.AtomicLong;
 
@@ -14,6 +15,10 @@ public class MovableState extends ObjectState {
     private transient int timeAlive;
     public final transient int damage = 15;
 
+    private MovableState() {
+        // kryo requires a no-args constructor to work properly
+    }
+
     public MovableState(long pid, double velocity) {
         super(24f, 24f, Vector2.Zero);
         this.heading = new Vector2(1, 0); // Unit vector

core/src/no/ntnu/trostespel/state/ObjectState.java

@@ -8,6 +8,10 @@ public class ObjectState {
     private transient Rectangle hitbox;
     private volatile Vector2 position;
 
+    private ObjectState() {
+        // kryo requires a no-args constructor to work properly
+    }
+
     public ObjectState(float x, float y, Vector2 position) {
         this.hitbox = new Rectangle(0, 0, x, y);
         this.position = position;

core/src/no/ntnu/trostespel/state/PlayerState.java

@@ -21,8 +21,9 @@ public class PlayerState extends ObjectState{
     private long timeOfDeath;
     private String username;
 
-    public PlayerState() {
+    private PlayerState() {
         super(72, 90, new Vector2(55, 55));
+        // kryo requires a no-args constructor to work properly
     }
 
     public PlayerState(long pid) {