Merge pull request 'Fix null pointer exception' (#92) from simplify-tracer into master

Reviewed-by: Chaoscaot <chaoscaot444@gmail.com>

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

@@ -93,7 +93,7 @@ public class TraceManager {
         }
         int frameID = trace.getFrameID();
         ShowManager.traceRemove(id);
-        frameMap.get(frameID).remove((Integer) id);
+        if (frameMap.containsKey(frameID)) frameMap.get(frameID).remove((Integer) id);
         testRemoveFrame(frameID);
     }
 }