[gnome-control-center] sound: clear the value on level_bar when stream is empty

[Robert Ancell <rancell src gnome org>]

commit aa0adcaa36701bf734f8eb4353ab655a15f81697
Author: Hui Wang <hui wang canonical com>
Date:   Tue Jan 4 16:17:28 2022 +0800

    sound: clear the value on level_bar when stream is empty
    
    We met an Input Device level_bar display issue on a machine which has
    no internal mic. At first there is no external mic plugged, so the
    Input Device list is empty and level_bar is gray color, after we plug
    an external mic, the level_bar has red color ripples, then we unplug
    the external mic, the Input Device list changes to empty and we
    expect the level_bar changes back to gray color, but some bars are
    still red color.
    
    Here clear the self->value to 0 if the stream is empty, then the
    level_bar will change back to gray color when Input/Output device
    list is empty.
    
    Signed-off-by: Hui Wang <hui wang canonical com>

 panels/sound/cc-level-bar.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/panels/sound/cc-level-bar.c b/panels/sound/cc-level-bar.c
index afecff53e..863613238 100644
--- a/panels/sound/cc-level-bar.c
+++ b/panels/sound/cc-level-bar.c
@@ -242,6 +242,7 @@ cc_level_bar_set_stream (CcLevelBar     *self,
 
   if (stream == NULL)
    {
+     self->value = 0.0;
      gtk_widget_queue_draw (GTK_WIDGET (self));
      return;
    }