[baobab] Check handler was set before disconnecting

[Paolo Borelli <pborelli src gnome org>]

commit 4481c2895787d6839244b44d4b992551b7a278c6
Author: Paolo Borelli <pborelli gnome org>
Date:   Tue Jul 31 12:16:43 2012 +0200

    Check handler was set before disconnecting

 src/baobab-window.vala |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)
---
diff --git a/src/baobab-window.vala b/src/baobab-window.vala
index 200991f..7e1ba70 100644
--- a/src/baobab-window.vala
+++ b/src/baobab-window.vala
@@ -507,7 +507,10 @@ namespace Baobab {
 
             set_model (active_location.scanner);
 
-            scanner.disconnect (scan_completed_handler);
+            if (scan_completed_handler > 0) {
+                scanner.disconnect (scan_completed_handler);
+            }
+
             scan_completed_handler = scanner.completed.connect(() => {
                 set_ui_state (UIPage.RESULT, false);
                 try {