Fix some NPE's

Signed-off-by: yoyosource <yoyosource@nidido.de>

BauSystem_Main/src/de/steamwar/bausystem/features/simulator/TNTSimulator.java

@@ -88,14 +88,22 @@ public class TNTSimulator {
     }
 
     public void show(Player player) {
+        if (!players.contains(player)) {
             entityServer.addPlayer(player);
             players.add(player);
         }
+    }
 
     public void hide(Player player) {
+        if (players.contains(player)) {
             entityServer.removePlayer(player);
             players.remove(player);
         }
+    }
+
+    void _hide(Player player) {
+        players.remove(player);
+    }
 
     public List<REntity> getEntities() {
         return tntElementList.stream().flatMap(element -> element.getEntities().stream()).collect(Collectors.toList());

BauSystem_Main/src/de/steamwar/bausystem/features/simulator/TNTSimulatorListener.java

@@ -88,6 +88,9 @@ public class TNTSimulatorListener implements Listener {
     @EventHandler
     public void onPlayerQuit(PlayerQuitEvent event) {
         SimulatorCursor.hide(event.getPlayer(), null);
+        SimulatorStorage.getSimulatorNames().forEach(s -> {
+            SimulatorStorage.getSimulator(s)._hide(event.getPlayer());
+        });
     }
 
     @EventHandler