[PATCH] Patch for feasible divide by zero

Static analysis (coverity) detected a feasible (although
not likely) code path such that the variables testEdges
and testNotEdges could be zero, which would result in
a divide by zero.  Add in a check for the zero case.

Fixes coverity 746806 and 746807

Fixes #11596.

Signed-off-by: Chris Pinkham <cpinkham@mythtv.org>