What should I do to run bubble sort?

I want to make bubble sort algorithm and I get this error. How to solve it?

    .data

    .text
    main:

            add     $s0, $s0, $0
    Loop1:  slti    $t0, $s0, 5
            bne     $t0, $0, Loop2
            j       Exit

    Loop2:  addi    $s1, $s0, 1
            slti    $t1, $s1, 5
            bne     $t1, $0, check
            j       Loop1

    check:  sll     $t2, $s0, 2     
            add     $t2, $t2, $s6   
            lw      $s2, 0($t2)            #Line 18
            add     $t3, $0, $s2        
            sll     $t4, $s1, 2     
            add     $t4, $t4, $s6       
            lw      $t4, 0($t4)     
            slt     $t5, $t4, $t3
            bne     $t5, $0, swap

    swap:   sw      $t4, 0($t3)
            sw      $s2, 0($t4)
            j       Loop2

Exit:

line 18: Runtime exception at 0x00400028: address out of range 0x00000000