return null instead of 0, 0 for selection if it can't be found

This should change the way in which getSelection() handles cases in which it cannot find a selection using the mechanisms in place (which happens every once in a while)

This way, instead of resetting to a Range(0, 0) it doesn't touch selection at all.

This may be considered "incorrect behavior" however, if it was intentional for a reset to `0,0` if nothing else could be done