how to resolve (-215:Assertion failed) !_src.empty() in function 'cv::boxFilter'

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Hello everyone, I am creating a system for object recognition, more precisely for license plates, it is for a control system for the beach in my city. I'm using Java and the latest version of OpenCv 4.3.0, I can open the camera without errors. The problem is in the code for plate recognition, it's giving errors, but it's about the version or something. I will leave the code of the classes, and the errors, I hope someone can help me. ENTRY CLASS

public class entrada {
    public static void main(String[] args) {
        try {
            // carregando a biblioteca
            System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
            System.out.println("começando");
            int[] mm = { 10,100 };
            int[] nn = { 10,100,300 };
            int[] aa = { 1 };
            int[] bb = { 5};
            int[] cc = { 5,10,15 };
            int[] dd = { 3 };
            int[] ee = {200};
            for (int m = 0; m < mm.length; m++) {
             for (int n = 0; n < nn.length; n++) {
              for (int a = 0; a < aa.length; a++) {
               for (int b = 0; b < bb.length; b++) {
                for (int c = 0; c < cc.length; c++) {
                 for (int d = 0; d < dd.length; d++) {
                  for(int e = 0; e < ee.length;e++){
                     // carregando a imagem original, ja em escala de cinza
                     Mat imageGray = Imgcodecs.imread("C:\\Users\\PC\\Desktop\\placa.jpg\"");
                     BufferedImage temp = reconhecimento.reconhecedorPlaca(imageGray, 
                            mm[m], nn[n], aa[a], bb[b], cc[c], dd[d],ee[e]);

                      File outputfile = new File("final" + aa[a]
                       + "x" + bb[b] + "x" + cc[c] + "x" + dd[d] + "x" +ee[e]
                        +"x"+ ".jpg");

                       ImageIO.write(temp, "jpg", outputfile);
            }}}}}}}
        } catch (IOException e) {
        System.out.println("Error: " + e.getMessage());
    }
}

CLASSE 2

public class reconhecimento {


 public static int ver =0;
 public static BufferedImage reconhecedorPlaca(Mat matrix,int m,int n,int a,int b,int c,int d,int e ) {

     int cols = matrix.cols();
     int rows = matrix.rows();

     int elemSize = (int)matrix.elemSize();

     byte[] data = new byte[cols * rows * elemSize];

     int type;

     Mat imagemResultanteCanny = new  Mat(matrix.rows(),matrix.cols(),CvType.CV_8UC1);

     Imgproc.blur(matrix, imagemResultanteCanny,new Size(3,3));
     Imgproc.Canny(imagemResultanteCanny, imagemResultanteCanny, m, n, 3, true);
     Imgcodecs.imwrite("canny"+m+"x"+n+"x3ver"+ver+".jpg", imagemResultanteCanny);
     ver++;

     Mat lines = new Mat();
     Imgproc.HoughLinesP(imagemResultanteCanny, lines, 2, Math.PI/180, b, c, d);
     System.out.println(lines.size());

     for (int x = 0; x < lines.cols(); x++)
     {
         double[] vec = lines.get(0, x);

         org.opencv.core.Point start = new org.opencv.core.Point();
         start.x = (int) vec[0];
         start.y = (int) vec[1];

         org.opencv.core.Point end = new org.opencv.core.Point();
         end.x = (int) vec[2];
         end.y = (int) vec[3];

         Imgproc.line(matrix, start, end, new Scalar(255,255,255), 2); 
     }



    Mat imagemResultanteCorner = new Mat();

     Imgproc.cornerHarris(imagemResultanteCanny, imagemResultanteCorner, 2, 3, 0.04, 1);

     Mat n_norm = new Mat();
     normalize(imagemResultanteCorner, n_norm,0,255,Core.compareTo(Core),CvType.CV_32FC1);
    Mat s_norm = new Mat();
     //Imgproc.conveScaleAbs(n_norm, s_norm);
     Imgcodecs.imwrite("corner"+m+"x"+n+"x"+a+"x"+b+"x"+c+"x"+d+"x"+e+"ver"+ver+".jpg",s_norm ...