Unaligned tab character offsets mouse position in current line

[lunathir]

I did some testing with this as I've had a bit of trouble with the mouse cursor not actually lining up to where I was clicking, and it turns out that any tab character will introduce an offset depending on how far the tab character is in the line. If it's at the beginning of the line it works perfectly, but if it's set at any point past a multiple of four it will be offset by that amount of characters.