We're getting check output that's not helpful

check-cpu-usage OK: NaN% CPU usage | cpu_idle=NaN, cpu_system=NaN, cpu_user=+Inf, cpu_nice=NaN, cpu_iowait=NaN, cpu_irq=NaN, cpu_softirq=NaN, cpu_steal=NaN, cpu_guest=NaN, cpu_guestnice=NaN

It seems that the check is not safe from dividing by zero.