[gnome-shell] Panel: fix finding leftmost and rightmost buttons

[Giovanni Campagna <gcampagna src gnome org>]

commit d9c3b83d1ed4e5b04d4ef36e383b206203d5370d
Author: Giovanni Campagna <gcampagna src gnome org>
Date:   Tue Jul 17 19:27:43 2012 +0200

    Panel: fix finding leftmost and rightmost buttons
    
    Previous code would access the array element before checking that
    the index was within bounds, and therefore cause a TypeError.
    It wasn't noticed earlier because at least one visible children
    is in each panel box in all session modes.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=619955

 js/ui/panel.js |   18 ++++++++++--------
 1 files changed, 10 insertions(+), 8 deletions(-)
---
diff --git a/js/ui/panel.js b/js/ui/panel.js
index c969381..648a677 100644
--- a/js/ui/panel.js
+++ b/js/ui/panel.js
@@ -753,10 +753,11 @@ const PanelCorner = new Lang.Class({
             return null;
 
         // Start at the back and work backward
-        let index = children.length - 1;
-        while (!children[index].visible && index >= 0)
-            index--;
-
+        let index;
+        for (index = children.length - 1; index >= 0; index--) {
+            if (children[index].visible)
+                break;
+        }
         if (index < 0)
             return null;
 
@@ -777,10 +778,11 @@ const PanelCorner = new Lang.Class({
             return null;
 
         // Start at the front and work forward
-        let index = 0;
-        while (!children[index].visible && index < children.length)
-            index++;
-
+        let index;
+        for (index = 0; index < children.length; index++) {
+            if (children[index].visible)
+                break;
+        }
         if (index == children.length)
             return null;