Interpolated var access is sometimes -1

[marchc1]

In InterpolatedVar.cs, changed by 1348c82:

private int WrapRange(int i) {
	return MathLib.Modulo(i, maxElement); // TODO: Why does -1 get passed here sometimes. We shouldn't have to change this to accomodate.
}

This should actually be

return (i >= maxElement) ? (i - maxElement) : i;

But for some reason, i coming in can sometimes be -1 when coming from here:

	public ref T this[int i] {
		get {
			Assert(IsIdxValid(i));
			i += firstElement;
			i = WrapRange(i);
			return ref elements![i];
		}
	}

There is a check for this (IsIdxValid), but it's just an assert. This must be some bug in my implementation I would imagine, but further research is needed. For now, the modulo works with an occasional hiccup.