[gnome-shell-extensions] windowsNavigator: fix work with 2.91.92 on multimonitor

[Maxim Ermilov <mermilov src gnome org>]

commit e0f27e94968e71ca3bbb7b5549c2b7b03ddb8255
Author: Maxim Ermilov <zaspire rambler ru>
Date:   Sat Mar 26 18:40:16 2011 +0300

    windowsNavigator: fix work with 2.91.92 on multimonitor

 extensions/windowsNavigator/extension.js |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/extensions/windowsNavigator/extension.js b/extensions/windowsNavigator/extension.js
index 0329770..6cd5374 100644
--- a/extensions/windowsNavigator/extension.js
+++ b/extensions/windowsNavigator/extension.js
@@ -165,7 +165,7 @@ function main() {
         this._text.raise_top();
     });
     injectToFunction(Workspace.Workspace.prototype, '_init', function(metaWorkspace) {
-        if (metaWorkspace.index() < 9) {
+        if (metaWorkspace && metaWorkspace.index() < 9) {
             this._tip = new St.Label({ style_class: 'extension-windowsNavigator-window-tooltip',
                                        visible: false });