hamburger-animation() not working: No items for 'nth'

[smichaelsen]

hamburger-generator() work great but when I use hamburger-animation() I get the following error on the console:

Error: List index is 1 but list has no items for `nth'
    on line 68 of project/sass/lib/_hamburger-icon.scss, in `hamburger-animation'
    from line 37 of project/sass/style.scss
    from line 11 of project/sass/main.scss
  Use --trace for backtrace.
Warning: Exited with error code 65 Use --force to continue.

This is how I call it:

.menu-icon {
  span {
    @include hamburger-generator($_width, $_thickness, $_gap, $color: $_color, $timing-function: linear);
  }
  float: left;
  margin-top: rem-calc(12);
}
nav.open .menu-icon span {
  @include hamburger-animation();
}

When I patch the hamburger-animation() mixin so that I can set $width and $gutter explicitly per argument instead of getting them from $hamburger-settings everything is fine, but it was better if your solution worked.

[mrmlnc]

This problem is specific to the official compiler. When using libSass it does not arise. I changed the declaration of global variables. Aaaaaaand It works!