OpenCV + Darknet+YOLOv3 problem

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In OpenCV3.4.3 use YOLOv3 model emerging questions : This is my code:

String modelConfiguration = "models/digital.cfg";
String modelWeights = "models/digital.weights";
fprintf(fp, "->readNetFromDarknet Start.\n");
Net net = readNetFromDarknet(modelConfiguration, modelWeights);
net.setPreferableBackend(DNN_BACKEND_OPENCV);
net.setPreferableTarget(DNN_TARGET_CPU);;
Mat blob,Input;
resize(_srcImg,Input,Size(416, 416));
blobFromImage(Input, blob, 1/255.0, cvSize(416, 416), Scalar(0,0,0), true, false);
net.setInput(blob);
vector<Mat> outs;
net.forward(outs, GetOutputsNames(net));

The following errors occur when running to "net.forward(outs, GetOutputsNames(net));":

 OpenCV(3.4.3) F:\opencv\opencv-3.4.3\opencv\sources\modules\core\src\matrix.cpp:367: error: (-215:Assertion failed) u != 0 in function 'cv::Mat::create';

The path is right. Sometimes it can be identified, sometimes not. Please help me see why. Thank you.