invalid reference fix

md5.js

/*
 * http://www.myersdaily.org/joseph/javascript/md5-text.html
 */
(function (global) {

  var md5cycle = function (x, k) {
    var a = x[0],
      b = x[1],
      c = x[2],
      d = x[3];

    a = ff(a, b, c, d, k[0], 7, -680876936);
    d = ff(d, a, b, c, k[1], 12, -389564586);
    c = ff(c, d, a, b, k[2], 17, 606105819);
    b = ff(b, c, d, a, k[3], 22, -1044525330);
    a = ff(a, b, c, d, k[4], 7, -176418897);
    d = ff(d, a, b, c, k[5], 12, 1200080426);
    c = ff(c, d, a, b, k[6], 17, -1473231341);
    b = ff(b, c, d, a, k[7], 22, -45705983);
    a = ff(a, b, c, d, k[8], 7, 1770035416);
    d = ff(d, a, b, c, k[9], 12, -1958414417);
    c = ff(c, d, a, b, k[10], 17, -42063);
    b = ff(b, c, d, a, k[11], 22, -1990404162);
    a = ff(a, b, c, d, k[12], 7, 1804603682);
    d = ff(d, a, b, c, k[13], 12, -40341101);
    c = ff(c, d, a, b, k[14], 17, -1502002290);
    b = ff(b, c, d, a, k[15], 22, 1236535329);

    a = gg(a, b, c, d, k[1], 5, -165796510);
    d = gg(d, a, b, c, k[6], 9, -1069501632);
    c = gg(c, d, a, b, k[11], 14, 643717713);
    b = gg(b, c, d, a, k[0], 20, -373897302);
    a = gg(a, b, c, d, k[5], 5, -701558691);
    d = gg(d, a, b, c, k[10], 9, 38016083);
    c = gg(c, d, a, b, k[15], 14, -660478335);
    b = gg(b, c, d, a, k[4], 20, -405537848);
    a = gg(a, b, c, d, k[9], 5, 568446438);
    d = gg(d, a, b, c, k[14], 9, -1019803690);
    c = gg(c, d, a, b, k[3], 14, -187363961);
    b = gg(b, c, d, a, k[8], 20, 1163531501);
    a = gg(a, b, c, d, k[13], 5, -1444681467);
    d = gg(d, a, b, c, k[2], 9, -51403784);
    c = gg(c, d, a, b, k[7], 14, 1735328473);
    b = gg(b, c, d, a, k[12], 20, -1926607734);

    a = hh(a, b, c, d, k[5], 4, -378558);
    d = hh(d, a, b, c, k[8], 11, -2022574463);
    c = hh(c, d, a, b, k[11], 16, 1839030562);
    b = hh(b, c, d, a, k[14], 23, -35309556);
    a = hh(a, b, c, d, k[1], 4, -1530992060);
    d = hh(d, a, b, c, k[4], 11, 1272893353);
    c = hh(c, d, a, b, k[7], 16, -155497632);
    b = hh(b, c, d, a, k[10], 23, -1094730640);
    a = hh(a, b, c, d, k[13], 4, 681279174);
    d = hh(d, a, b, c, k[0], 11, -358537222);
    c = hh(c, d, a, b, k[3], 16, -722521979);
    b = hh(b, c, d, a, k[6], 23, 76029189);
    a = hh(a, b, c, d, k[9], 4, -640364487);
    d = hh(d, a, b, c, k[12], 11, -421815835);
    c = hh(c, d, a, b, k[15], 16, 530742520);
    b = hh(b, c, d, a, k[2], 23, -995338651);

    a = ii(a, b, c, d, k[0], 6, -198630844);
    d = ii(d, a, b, c, k[7], 10, 1126891415);
    c = ii(c, d, a, b, k[14], 15, -1416354905);
    b = ii(b, c, d, a, k[5], 21, -57434055);
    a = ii(a, b, c, d, k[12], 6, 1700485571);
    d = ii(d, a, b, c, k[3], 10, -1894986606);
    c = ii(c, d, a, b, k[10], 15, -1051523);
    b = ii(b, c, d, a, k[1], 21, -2054922799);
    a = ii(a, b, c, d, k[8], 6, 1873313359);
    d = ii(d, a, b, c, k[15], 10, -30611744);
    c = ii(c, d, a, b, k[6], 15, -1560198380);
    b = ii(b, c, d, a, k[13], 21, 1309151649);
    a = ii(a, b, c, d, k[4], 6, -145523070);
    d = ii(d, a, b, c, k[11], 10, -1120210379);
    c = ii(c, d, a, b, k[2], 15, 718787259);
    b = ii(b, c, d, a, k[9], 21, -343485551);

    x[0] = add32(a, x[0]);
    x[1] = add32(b, x[1]);
    x[2] = add32(c, x[2]);
    x[3] = add32(d, x[3]);

  }

  var cmn = function (q, a, b, x, s, t) {
    a = add32(add32(a, q), add32(x, t));
    return add32((a << s) | (a >>> (32 - s)), b);
  }

  var ff = function (a, b, c, d, x, s, t) {
    return cmn((b & c) | ((~b) & d), a, b, x, s, t);
  }

  var gg = function (a, b, c, d, x, s, t) {
    return cmn((b & d) | (c & (~d)), a, b, x, s, t);
  }

  var hh = function (a, b, c, d, x, s, t) {
    return cmn(b ^ c ^ d, a, b, x, s, t);
  }

  var ii = function (a, b, c, d, x, s, t) {
    return cmn(c ^ (b | (~d)), a, b, x, s, t);
  }

  var md51 = function (s) {
    var txt = '',
      n = s.length,
      state = [1732584193, -271733879, -1732584194, 271733878],
      i;
    for (i = 64; i <= s.length; i += 64) {
      md5cycle(state, md5blk(s.substring(i - 64, i)));
    }
    s = s.substring(i - 64);
    var tail = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];
    for (i = 0; i < s.length; i++)
      tail[i >> 2] |= s.charCodeAt(i) << ((i % 4) << 3);
    tail[i >> 2] |= 0x80 << ((i % 4) << 3);
    if (i > 55) {
      md5cycle(state, tail);
      for (i = 0; i < 16; i++) tail[i] = 0;
    }
    tail[14] = n * 8;
    md5cycle(state, tail);
    return state;
  }

  /* there needs to be support for Unicode here,
   * unless we pretend that we can redefine the MD-5
   * algorithm for multi-byte characters (perhaps
   * by adding every four 16-bit characters and
   * shortening the sum to 32 bits). Otherwise
   * I suggest performing MD-5 as if every character
   * was two bytes--e.g., 0040 0025 = @%--but then
   * how will an ordinary MD-5 sum be matched?
   * There is no way to standardize text to something
   * like UTF-8 before transformation; speed cost is
   * utterly prohibitive. The JavaScript standard
   * itself needs to look at this: it should start
   * providing access to strings as preformed UTF-8
   * 8-bit unsigned value arrays.
   */
  var md5blk = function (s) { /* I figured global was faster.   */
    var md5blks = [],
      i; /* Andy King said do it this way. */
    for (i = 0; i < 64; i += 4) {
      md5blks[i >> 2] = s.charCodeAt(i) + (s.charCodeAt(i + 1) << 8) + (s.charCodeAt(i + 2) << 16) + (s.charCodeAt(i + 3) << 24);
    }
    return md5blks;
  }

  var hex_chr = '0123456789abcdef'.split('');

  var rhex = function (n) {
    var s = '',
      j = 0;
    for (; j < 4; j++)
      s += hex_chr[(n >> (j * 8 + 4)) & 0x0F] + hex_chr[(n >> (j * 8)) & 0x0F];
    return s;
  }

  var hex = function (x) {
    for (var i = 0; i < x.length; i++)
      x[i] = rhex(x[i]);
    return x.join('');
  }

  var md5 = global.md5 = function (s) {
    return hex(md51(s));
  }

  /* this function is much faster,
  so if possible we use it. Some IEs
  are the only ones I know of that
  need the idiotic second function,
  generated by an if clause.  */

  var add32 = function (a, b) {
    return (a + b) & 0xFFFFFFFF;
  }

  if (md5('hello') != '5d41402abc4b2a76b9719d911017c592') {
    var add32 = function (x, y) {
      var lsw = (x & 0xFFFF) + (y & 0xFFFF),
        msw = (x >> 16) + (y >> 16) + (lsw >> 16);
      return (msw << 16) | (lsw & 0xFFFF);
    }
  }

})(window);

Whats the purpose of txt on line 109?

Huh, it's never used, really weird