Fixed clear nullpointer

BauSystem_Main/src/de/steamwar/bausystem/features/tracer/TraceManager.java

@@ -152,7 +152,7 @@ public class TraceManager implements Listener {
                 .keySet()
                 .forEach(player -> {
                     Set<Player> players = followerMap.getOrDefault(player, Collections.emptySet());
-                    tracesByRegion.get(region).values().forEach(trace -> {
+                    tracesByRegion.getOrDefault(region, new HashMap<>()).values().forEach(trace -> {
                         trace.hide(player);
                         players.forEach(trace::hide);
                     });