Program: 56311
Project: 56311
Buggy source:
/** 
 * Starts listening at a already created server.
 * @return Yoke
 */
public Yoke listen(final HttpServer server){
  final boolean secure=server.isSSL();
  server.requestHandler(new Handler<HttpServerRequest>(){
    @Override public void handle(    HttpServerRequest req){
      final Map<String,Object> context=new HashMap<>(defaultContext);
      final YokeHttpServerRequest request=requestWrapper.wrap(req,secure,context,engineMap);
      new Handler<Object>(){
        int currentMiddleware=-1;
        @Override public void handle(        Object error){
          if (error == null) {
            currentMiddleware++;
            if (currentMiddleware < middlewareList.size()) {
              MountedMiddleware mountedMiddleware=middlewareList.get(currentMiddleware);
              if (request.path().startsWith(mountedMiddleware.mount)) {
                Middleware middlewareItem=mountedMiddleware.middleware;
                middlewareItem.handle(request,this);
              }
 else {
                handle(null);
              }
            }
 else {
              HttpServerResponse response=request.response();
              response.setStatusCode(404);
              response.setStatusMessage(HttpResponseStatus.valueOf(404).reasonPhrase());
              if (errorHandler != null) {
                errorHandler.handle(request,null);
              }
 else {
                response.end(HttpResponseStatus.valueOf(404).reasonPhrase());
              }
            }
          }
 else {
            request.put("String_Node_Str",error);
            if (errorHandler != null) {
              errorHandler.handle(request,null);
            }
 else {
              HttpServerResponse response=request.response();
              if (error instanceof Integer) {
                int code=(Integer)error;
                response.setStatusCode(code);
                response.setStatusMessage(HttpResponseStatus.valueOf(code).reasonPhrase());
                response.end(HttpResponseStatus.valueOf(code).reasonPhrase());
              }
 else {
                response.setStatusCode(500);
                response.setStatusMessage(HttpResponseStatus.valueOf(500).reasonPhrase());
                response.end(HttpResponseStatus.valueOf(500).reasonPhrase());
              }
            }
          }
        }
      }
.handle(null);
    }
  }
);
  return this;
}

Fixed version (ground truth):
/** 
 * Starts listening at a already created server.
 * @return Yoke
 */
public Yoke listen(final HttpServer server){
  final boolean secure=server.isSSL();
  server.requestHandler(new Handler<HttpServerRequest>(){
    @Override public void handle(    HttpServerRequest req){
      final Map<String,Object> context=new HashMap<>(defaultContext);
      final YokeHttpServerRequest request=requestWrapper.wrap(req,secure,context,engineMap);
      new Handler<Object>(){
        int currentMiddleware=-1;
        @Override public void handle(        Object error){
          if (error == null) {
            currentMiddleware++;
            if (currentMiddleware < middlewareList.size()) {
              MountedMiddleware mountedMiddleware=middlewareList.get(currentMiddleware);
              if (request.path().startsWith(mountedMiddleware.mount)) {
                Middleware middlewareItem=mountedMiddleware.middleware;
                middlewareItem.handle(request,this);
              }
 else {
                handle(null);
              }
            }
 else {
              HttpServerResponse response=request.response();
              response.setStatusCode(404);
              response.setStatusMessage(HttpResponseStatus.valueOf(404).reasonPhrase());
              if (errorHandler != null) {
                errorHandler.handle(request,null);
              }
 else {
                response.end(HttpResponseStatus.valueOf(404).reasonPhrase());
              }
            }
          }
 else {
            request.put("String_Node_Str",error);
            if (errorHandler != null) {
              errorHandler.handle(request,null);
            }
 else {
              HttpServerResponse response=request.response();
              int errorCode=500;
              if (response.getStatusCode() >= 400) {
                errorCode=response.getStatusCode();
              }
              if (error instanceof Integer) {
                errorCode=(Integer)error;
              }
              response.setStatusCode(errorCode);
              response.setStatusMessage(HttpResponseStatus.valueOf(errorCode).reasonPhrase());
              response.end(HttpResponseStatus.valueOf(errorCode).reasonPhrase());
            }
          }
        }
      }
.handle(null);
    }
  }
);
  return this;
}