Fix bug introduced in rev 1.142 with the additional/optional arguments to the

yesno() and noyes() methods:
We need to check the argument count before using the second (optional)
argument or else it has some garbage/left-over value from some previous JS
function call. And no, just increasing the argument count in the method table
isn't enough. :-(
Reported by echicken and DaiTengu, thanks!