Fix Divide by Zero bug in translateToPx()
Fix Divide by Zero bug in translateToPx()

Bug that drove me insane hunting down and fixing back in 2010.  Found
the bug is still in the latest version so I applied it to the latest
branch.  If I recall correctly it fails SILENTLY with no errors and
sliders that just don't work. Took days to initially find the problem.

madrobby/scriptaculous,madrobby/scriptaculous,madrobby/scriptaculous,pandoraui/scriptaculous,pandoraui/scriptaculous,pandoraui/scriptaculous