vol_perc: return zero if the value of max is set to zero

slstatus.c

@@ -501,6 +501,9 @@ vol_perc(const char *card)
 	snd_mixer_selem_id_free(s_elem);
 	snd_mixer_close(handle);
 
+	if (max == 0)
+		return smprintf("%d%%", 0);
+	else
 		return smprintf("%d%%", ((uint_fast16_t)(vol * 100) / max));
 }