maybe some bug in less 3.0.1

[lialosiu]

sorry for my poor English.... m(_ _ )m

this less (just an example):

@cols: 1, 2;

.a(@i: length(@cols)) when (@i > 0) {
  @divider: e(extract(@cols, @i));
}
.a;

.b(@j: 1) when (@j < length(@cols)) {
  @divider: e(extract(@cols, @j));
}
.b;

will cause exception in less 3.0.1

but in less 2.7.3, run so far so good.

maybe some bug at here?
exception throwed in this line:

less.js/lib/less/parser/parser-input.js

Line 67 in b873737

current = current.slice(length + parserInput.i - mem + curr);

because current is a number value 2:

any solution?