[cpu][mac] doesn't return error when cpu.frequency

cpu/cpu_darwin.go

@@ -87,10 +87,9 @@ func InfoWithContext(ctx context.Context) ([]InfoStat, error) {
 	// Use the rated frequency of the CPU. This is a static value and does not
 	// account for low power or Turbo Boost modes.
 	cpuFrequency, err := unix.SysctlUint64("hw.cpufrequency")
-	if err != nil {
-		return ret, err
-	}
+	if err == nil {
 		c.Mhz = float64(cpuFrequency) / 1000000.0
+	}
 
 	return append(ret, c), nil
 }