h4h5tools

Fix faults occurring when empty string is passed.
  - empty string is recognized as one element, which is incorrect
  - Fix
    - Before
     for (i = j = 0; j <= len; ++j)
       if (j == len || s[j] == ',')
    - After
     for (i = j = 0; j <= len; ++j)
       if ((j == len && len) || s[j] == ',')