What is best way to debug if we dont know the invalid index in XCOS?

  !--error 21 
Invalid index.
 
 
 do_eval: Error while calling block Kalman_Filter_IF [uid='65b73f57:18ea0a60c83:-7fdd']: invalid parameter (ier=21.000000, %scicos_prob= 
      %F). 

I know the error is in the below line of code are as :-1:

**[ok, x0_set, covariance_matrix, exprs] = scicos_getvalue("Set Properties and State", labels, types, exprs);**
function [x, y, typ] = Kalman_Filter_IF(job, arg1, arg2)
    x = [];
    y = [];
    typ = [];
    
    // Kalman filter initial state and covariance
    initial_state = [0.0; 0.0];                  // 2*1 matrix
    initial_covariance = [1.0, 0.0; 0.0, 1.0];  // 2*2 matrix 
    model.cpar = initial_covariance;  // Use covariance matrix as a parameter
    dis
    select job
        // Initialize with mask parameters if any
        case "set" then
            x = arg1;
            graphics = arg1.graphics;
            exprs = graphics.exprs;
            model = arg1.model;
            
            // Create a dialog for getting user inputs
            while %t do
                // Initialize dialog for parameters and initial state
                labels = ['Initial state [x_dot, x]', 'Covariance'];  // Changed 'Stiffness' to 'Covariance'
                types = list('vec', 2, 'mat', 2);  // Changed 'vec' to 'mat' for Covariance
                [ok, x0_set, covariance_matrix, exprs] = scicos_getvalue("Set Properties and State", labels, types, exprs);
                
                // Check return
                if ~ok then
                    break;
                end
                
                mess = [];
                
                // Check parameters
                // You can add additional checks for input parameters here if needed
                
                // Accept inputs and save them
                if ok then
                    // Concatenate the covariance matrix to the state vector
                    model.state = [x0_set; reshape(covariance_matrix,1,4)];  // Use the concatenation operator ":" for the matrix
                    graphics.exprs = exprs;
                    x.graphics = graphics;
                    x.model = model;
                    break;
                else
                    message("Failed to update block io");
                end
            end
            
        // Define block properties
        case "define" then
            // Create object
            model = scicos_model();
            
            // Provide name and type
            model.sim = list("Kalman_Filter_sim", 5);
            
            // Define inputs and outputs
            // One input with a variable-size "double" element
            model.in = 1; // it's only z
            model.in2 = 1;   // the second dimension of I/P
            model.intyp = 1;
            
            // One output with a single "double" element
            model.out = [2; 2];
            model.out2 = [1; 2];
            model.outtyp = 1;
            
            // Set initial state
            model.state = [initial_state; matrix(initial_covariance, 4, 1)];   // Use the matrix concatenation function
                                                                           // For example: [initial_state; initial_covariance(:)]
            
            // Set default parameter
            model.rpar = initial_covariance;  // Use the covariance matrix as a parameter
            
            // Define block properties
            model.blocktype = "c";
            model.dep_ut = [%t %f];
            
            // Set block properties
            exprs = ["[0.0; 0.0]"; "[1.0]"];
            x = standard_define([4 4], model, exprs);
            x.graphics.style = ["blockWithLabel;displayedLabel=Kalman_Filter"];
            
    end
endfunction


As you can see that until 27 it is printed but after that 28 is not printed so there is issue in this line. Help me to debug it.