[gnome-applets] Add a comment to explain the apparently unecessary change made at the last commit

[Callum McKenzie <callum src gnome org>]

commit 4bc831b13992342871984d68c048ce26b5b077d3
Author: Callum McKenzie <callum spooky-possum org>
Date:   Mon Jun 14 19:30:26 2010 +1200

    Add a comment to explain the apparently unecessary change made at the last commit

 mixer/applet.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/mixer/applet.c b/mixer/applet.c
index ac60d17..915376f 100644
--- a/mixer/applet.c
+++ b/mixer/applet.c
@@ -127,7 +127,8 @@ init_pixbufs (GnomeVolumeApplet *applet)
   for (n = 0; pix_filenames[n] != NULL; n++) {
     if (applet->pix[n]) {
       g_object_unref (applet->pix[n]);
-      applet->pix[n] = NULL;
+      applet->pix[n] = NULL; // gnome_icon_theme_load_icon can call us
+                             // recursively, so we have to be careful.
     }
 
     applet->pix[n] = gtk_icon_theme_load_icon (gtk_icon_theme_get_default (),