top: try avoiding the edge of a 'divide by zero' cliff

top: try avoiding the edge of a 'divide by zero' cliff

Darn, after testing on some older, out of date distros
I was embarrassed to find some awful code I created in
the commit shown below. I was rewarded with some 'nan'
floating point values and 'inf' computational results.

Reference(s);
. a missed opportunity to repent
commit 5c5bff392bfaf78b7bacb9b954c1fd1e9d818544
. true source of my original sin
commit 2d5b51d1a2aa19d077a2f3db5be187f982d70e70

Signed-off-by: Jim Warner <james.warner@comcast.net>