[gnome-todo] edit-pane: check if binding is still valid

[Victor Toso de Carvalho <victortoso src gnome org>]

commit 44a6a470903602d293d259a0b3ee4a70f83571d1
Author: Victor Toso <me victortoso com>
Date:   Sun Oct 2 23:40:25 2016 +0200

    edit-pane: check if binding is still valid
    
    It might not be valid on dispose:
    
     "The binding will automatically be removed when either the source or
      the target instances are finalized."
    
    https://bugzilla.gnome.org/show_bug.cgi?id=772178

 src/gtd-edit-pane.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/src/gtd-edit-pane.c b/src/gtd-edit-pane.c
index 9903e8a..780b99f 100644
--- a/src/gtd-edit-pane.c
+++ b/src/gtd-edit-pane.c
@@ -375,8 +375,10 @@ gtd_edit_pane_set_task (GtdEditPane *pane,
 
   if (priv->task)
     {
-      g_clear_pointer (&priv->notes_binding, g_binding_unbind);
-      g_clear_pointer (&priv->priority_binding, g_binding_unbind);
+      if (G_IS_BINDING (priv->notes_binding))
+        g_clear_pointer (&priv->notes_binding, g_binding_unbind);
+      if (G_IS_BINDING (priv->priority_binding))
+        g_clear_pointer (&priv->priority_binding, g_binding_unbind);
       g_signal_handlers_disconnect_by_func (gtk_text_view_get_buffer (priv->notes_textview),
                                             gtd_edit_pane__task_changed_cb, pane);
       g_signal_handlers_disconnect_by_func (priv->priority_combo,