It isn’t mandatory and the options isn’t even in the avast 8 settings, so I don’t know how you have managed to get it displayed.

If you previously had this option enabled in an earlier version of avast and you did an in program update then it would have been preserved as these settings would have been in the avast5.ini file. A clean install of avast 8 should have replaced the old avast5.ini file.

So I suspect that at some point in avast 7 you had this enabled and the avast5.ini file still has that information in it.