Please share any context you've got. The reading that makes the most sense to me is "you can't account for negligence", or word-for-word "a negligent person can't be accounted for".
(Thinking about this has made me forget the difference between "take into account" and "account for". I'm not sure which one works better in the sense of taking something into consideration ahead of time as a contingency measure. If it's the former then pretend I used it in this post!)
همل، يهمل = to neglect
هامل = "negligent person", literally reading "neglector"
عمل حساب (or حَسَب حساب) = account for [something]
عمل حساب لهامل = account for a negligent person
بِنعمل حساب لهامل = passive that literally reads "a negligent person is accounted for". However, we use it to express possibility, so it's understood to mean "a negligent person can be accounted for"
ما بنعمل حساب لهامل = literally reads "a negligent person is not accounted for", but again, it really means "a negligent person cannot be accounted for"