Fix double death error

Signed-off-by: Lixfel <agga-games@gmx.de>

FightSystem_Core/src/de/steamwar/fightsystem/record/PacketProcessor.java

@@ -223,7 +223,11 @@ public class PacketProcessor {
     private void entityDespawns() throws IOException {
         int entityId = source.readInt();
 
-        execSync(() -> REntity.getEntity(entityId).die());
+        execSync(() -> {
+            REntity entity = REntity.getEntity(entityId);
+            if(entity != null)
+                entity.die();
+        });
     }
 
     private void entitySneak() throws IOException {