[gnome-shell] AppDisplay: fix isTerminal() check for apps without categories

[Giovanni Campagna <gcampagna src gnome org>]

commit a4e019442f8613c45839cdf13117539b08b381ad
Author: Giovanni Campagna <gcampagna src gnome org>
Date:   Mon Jan 13 23:02:06 2014 +0100

    AppDisplay: fix isTerminal() check for apps without categories
    
    If there is no Categories line in the .desktop file, get_categories()
    returns null, not an empty array.

 js/ui/appDisplay.js |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/js/ui/appDisplay.js b/js/ui/appDisplay.js
index 049b339..2f5465b 100644
--- a/js/ui/appDisplay.js
+++ b/js/ui/appDisplay.js
@@ -48,7 +48,8 @@ const PAGE_SWITCH_TRESHOLD = 0.2;
 const PAGE_SWITCH_TIME = 0.3;
 
 function _isTerminal(app) {
-    return app.get_app_info().get_categories().indexOf('TerminalEmulator') > -1;
+    let categories = app.get_app_info().get_categories() || [];
+    return categories.indexOf('TerminalEmulator') > -1;
 }
 
 // Recursively load a GMenuTreeDirectory; we could put this in ShellAppSystem too