[tracker] tracker-needle: Fix crash in result store

[Carlos Garnacho <carlosg src gnome org>]

commit 846a541fcb1b0b3b6f9d78254bec873eddebebce
Author: Carlos Garnacho <carlos lanedo com>
Date:   Tue Oct 18 14:32:55 2011 +0200

    tracker-needle: Fix crash in result store
    
    n_children() would crash if there weren't any items
    in the categories array. Fixes GB#661446, reported by
    Damien Gombault <desintegr gmail com>

 src/tracker-needle/tracker-result-store.vala |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)
---
diff --git a/src/tracker-needle/tracker-result-store.vala b/src/tracker-needle/tracker-result-store.vala
index 4e5f22a..e3a11f6 100644
--- a/src/tracker-needle/tracker-result-store.vala
+++ b/src/tracker-needle/tracker-result-store.vala
@@ -690,8 +690,10 @@ public class Tracker.ResultStore : Gtk.TreeModel, GLib.Object {
 		if (iter == null) {
 			if (queries.length > 1) {
 				return categories.length - 1;
-			} else {
+			} else if (categories.length > 0) {
 				return categories[0].count;
+			} else {
+				return -1;
 			}
 		}