Fix SignEdit NPE

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

BauSystem_Main/src/de/steamwar/bausystem/features/world/SignEdit.java

@@ -58,7 +58,7 @@ public class SignEdit implements Listener {
     @EventHandler
     public void editSign(PlayerInteractEvent event) {
         if (!event.getPlayer().isSneaking()) return;
-        if (!event.getClickedBlock().getType().name().contains("SIGN")) return;
+        if (event.getClickedBlock() == null || !event.getClickedBlock().getType().name().contains("SIGN")) return;
 
         if (event.getAction() == Action.RIGHT_CLICK_BLOCK && (event.getItem() == null || event.getItem().getType() == Material.AIR)) {
             event.setCancelled(true);