Issue with Deprecated Division warning in SASS - math

Question

I am doing a large project converting old SASS code (specifically node-sass), into the newer SASS using the SASS npm package, and I am getting this error message
DEPRECATION WARNING: Using / for division is deprecated and will be removed in Dart Sass 2.0.0. Recommendation: math.div(3, 4)
However, it seems to relate to this line of code
$_this: nth($short, $_i);
I am finding this confusing as I am not trying to divide the numbers, and the aren't separated by a /, can someone explain please, or at least help me with a solution, as ignoring the line isn't working either?
If it helps anyone, I have included the whole statement now...
#function parse-span(
$short,
$key: span
) {
$_return: ();
#if type-of($short) == map {
$_return: $short;
} #else {
$_at: index($short, at);
#if $_at {
$_loci: $_at + 1;
$_location: nth($short, $_loci);
$_return: map-merge($_return, (location: $_location));
$short: set-nth($short, $_at, null);
$short: set-nth($short, $_loci, null);
}
$_i: 1;
$_span: ();
#while $_i <= length($short) {
$_this: nth($short, $_i); <--- faulty line?
#if type-of($_this) == number {
$_span: append($_span, $_this);
$short: set-nth($short, $_i, null);
} #else if $_this == of {
$short: set-nth($short, $_i, null);
$_i: length($short) + 1;
}
$_i: $_i + 1;
}
#if length($_span) > 0 {
$_span: if(length($_span) == 1, nth($_span, 1), $_span);
$_return: map-merge($_return, ($key: $_span));
}
$_return: map-merge($_return, parse-grid($short));
}
#return $_return;
}
$_gutters: parse-span($short, gutter-override);
I have tried the solution in the comments but to no resolution.
Here is an image of the actual warning