[gnome-shell] LookingGlass: fix a Clutter warning

[Giovanni Campagna <gcampagna src gnome org>]

commit 856207c15459a2d86b2790e59eb2619cd1d77a21
Author: Giovanni Campagna <gcampagna src gnome org>
Date:   Tue Jan 11 21:14:16 2011 +0100

    LookingGlass: fix a Clutter warning
    
    After destroying an actor, it is no more parented anywhere, so we
    cannot allocate it.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=633028

 js/ui/lookingGlass.js |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/js/ui/lookingGlass.js b/js/ui/lookingGlass.js
index 60bab9b..2f89436 100644
--- a/js/ui/lookingGlass.js
+++ b/js/ui/lookingGlass.js
@@ -398,6 +398,9 @@ Inspector.prototype = {
     },
 
     _allocate: function(actor, box, flags) {
+        if (!this._eventHandler)
+            return;
+
         let primary = global.get_primary_monitor();
 
         let [minWidth, minHeight, natWidth, natHeight] =
@@ -415,6 +418,7 @@ Inspector.prototype = {
         Clutter.ungrab_pointer(this._eventHandler);
         Clutter.ungrab_keyboard(this._eventHandler);
         this._eventHandler.destroy();
+        this._eventHandler = null;
         this.emit('closed');
     },