[folks] tpf: don't unprepare the backend if it isn't prepared

[Raul Gutierrez Segales <raulgs src gnome org>]

commit 2e81215dc900c0697d14f31805db06580dfc5a15
Author: Raul Gutierrez Segales <rgs collabora co uk>
Date:   Wed Sep 21 20:25:54 2011 +0100

    tpf: don't unprepare the backend if it isn't prepared

 backends/telepathy/tp-backend.vala |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/backends/telepathy/tp-backend.vala b/backends/telepathy/tp-backend.vala
index b041675..987ac0f 100644
--- a/backends/telepathy/tp-backend.vala
+++ b/backends/telepathy/tp-backend.vala
@@ -125,6 +125,9 @@ public class Folks.Backends.Tp.Backend : Folks.Backend
    */
   public override async void unprepare () throws GLib.Error
     {
+      if (!this._is_prepared)
+        return;
+
       this._account_manager.account_enabled.disconnect (
           this._account_enabled_cb);
       this._account_manager.account_validity_changed.disconnect (