Changing values of an array but ending up with the last two values being duplicates

Question

A piece of a program i am writing replaces a certain value in an array with the next value in the array. However, it ends up with the last two values in the array being identical. Is there a way to just replace the last value with NULL?

this is the current output

found it again
Array value 0: cat:
Array value 1: file1.txt:
Array value 2: output.txt:
Array value 3: output.txt:
Array value 4: (null):
Array value 5: (null):
This is the first line in file1.txt
This is the last line

this is the output when i try to replace the last value will null, but it returns a segmentation fault

found it again
Array value 0: cat:
Array value 1: file1.txt:
Array value 2: output.txt:
Array value 3: (null):
Array value 4: (null):
Array value 5: (null):

here is the full code

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <string.h>

#define BUFFERSIZE 1024

int main(int argc, char* argv[])
{
    int fd_out = dup(STDOUT_FILENO);
    int fd_in = dup(STDIN_FILENO);
    
    argc++;

    char buf[BUFFERSIZE];
    int n;
        printf("Please enter commands: \n");

    while ((n = read(STDIN_FILENO, buf, BUFFERSIZE)) > 0)
        {
        buf[n] = 0;
        buf[strlen(buf)-1] = '\0';
        int i = 0;
        char* array[10];
        char* token1 = strtok(buf, " ");

        while ((token1 != NULL))
        {
            array[i++] = token1;
            token1 = strtok(NULL, " ");
            
        }//while

        array[i] = NULL;

        if (strcmp(buf, "exit") == 0)
        {
            break;
        }//if
        
        for (int j = 0; j < i; j++) 
        {
            if (!strcmp(array[j], ">"))
            {
                char* filename_out = array[j+1];
                printf("STDOUT redirected\n");
                printf("found it\n");
                int file_out = open(filename_out, O_WRONLY | O_CREAT, 0777);
                int file2_out = dup2(file_out, 1);
                
                for(int k = j; k < i-1; k++)
                {
                    array[k] = array[k + 1];
                }//if
                
                array[i] = NULL;
                printf("found it again\n");

                if ((file_out | file2_out) == -1)
                {
                    return 1;
                }//if

                //array[i-1] = NULL;

                            for (int j = 0; j < i+2; j++)
                            {
                                    printf("Array value %d: %s:\n", j, array[j]);
                            }//for*/
            }//if
            if (!strcmp(array[j], "<"))
            {
                char* filename_in = array[j+1];
                printf("STDIN_FILENO redirected\n");
                int file_in = open(filename_in, O_WRONLY | O_CREAT, 0777);
                int file2_in = dup2(file_in, 0);

                                for(int l = j; l < i - 1; l++)
                                {
                                        array[l] = array[l + 1];
                                }//for
                
                if ((file_in | file2_in) == -1)
                {
                    return 1;
                }//if
            }
        }//for

            for (int i = 1; i < argc; i++)
            {
            pid_t pid;
            
            if (argc >= 1) 
            {
                if ((pid = fork()) < 0) 
                {
                    perror("fork");
                }//if
                else if (pid == 0) 
                { // child process
                    if (execvp(array[0], array) == -1) 
                    {
                        perror("execvp");
                        return EXIT_FAILURE;
                    } // if
                }//else if
                else 
                {   // parent process
                    int status;
                    wait(&status);
                    //int again_out = dup2(fd_out, 1);
                    //int again_in = dup2(fd_in, 0);
                    if ((again_out | again_in) == -1)
                    {
                        return 1;
                    }
                    printf("Please enter commands again: \n");
                    
                }//else     
            }//if
            else 
            {
                fprintf(stderr, "Please specify the name of the program to exec as a command line argument\n");
                return EXIT_FAILURE;
            }//if
        }//for
    }//while
    if (n == -1) perror("read");
}//main

i tried to use array[i-1] = NULL; (where i is the size of the array) but it returns a segmentation fault