can you clarify this a little?  It seems like if the value is numeric and less than 0 we either have a sucky invariant or are encountering an invariant violation.  This seems more likely to protect us against undefined in the pipeline somehow since "undefined > -1" is false.

One option here I think is just to say "// Paranoia; our value should never be negative and let's never clobber this to undefined."  (I'm okay with us having a few of these as long as it's clear we're just doing defensive programming under time constraints and that in a perfect world we'll have an assertion guard or just trace the code-path and have unit tests to ensure such things never happen.)