Removed null returns

BauSystem_Main/src/de/steamwar/bausystem/features/tracer2/TraceManager.java

@@ -85,8 +85,11 @@ public class TraceManager implements Listener {
      * @param id id of the trace
      * @return the trace with given id or null if no trace with id is found
      */
-    public Trace get(int id){
+    public Optional<Trace> get(int id){
-        return traces.getOrDefault(id, null);
+        Trace ret = traces.get(id);
+        if(traces.containsKey(id))
+            return  Optional.of(traces.get(id));
+        return Optional.empty();
     }
 
     /** Methode to get all traces