[gtksourceview] Completion: fix critical message

[Sébastien Wilmet <swilmet src gnome org>]

commit c468ee5b2c45a4fdce46e4fb6f8a7f7b3d10b328
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Thu Oct 16 16:53:41 2014 +0200

    Completion: fix critical message

 gtksourceview/gtksourcecompletion.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)
---
diff --git a/gtksourceview/gtksourcecompletion.c b/gtksourceview/gtksourcecompletion.c
index 40b1619..38b8075 100644
--- a/gtksourceview/gtksourcecompletion.c
+++ b/gtksourceview/gtksourcecompletion.c
@@ -699,8 +699,9 @@ gtk_source_completion_activate_proposal (GtkSourceCompletion *completion)
 
        activated = gtk_source_completion_provider_activate_proposal (provider, proposal, &insert_iter);
 
-       valid_context = gtk_source_completion_context_get_iter (completion->priv->context,
-                                                               &context_iter);
+       valid_context = (completion->priv->context != NULL &&
+                        gtk_source_completion_context_get_iter (completion->priv->context,
+                                                                &context_iter));
 
        if (!activated && valid_context)
        {