[gtk+] searchenginetracker: ensure nie:url is bound

[Carlos Garnacho <carlosg src gnome org>]

commit 61d6c1a523385cc1fe724cbe1cc8ad9545e6cc43
Author: Carlos Garnacho <carlosg gnome org>
Date:   Fri Nov 20 19:02:17 2015 +0100

    searchenginetracker: ensure nie:url is bound
    
    This could produce strange warnings as it is currently passed to
    tracker:uri-is-* sparql functions, as these expect no NULLs.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=758407

 gtk/gtksearchenginetracker.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gtk/gtksearchenginetracker.c b/gtk/gtksearchenginetracker.c
index f284a3c..31da508 100644
--- a/gtk/gtksearchenginetracker.c
+++ b/gtk/gtksearchenginetracker.c
@@ -354,7 +354,7 @@ gtk_search_engine_tracker_start (GtkSearchEngine *engine)
   sparql_append_string_literal (sparql, search_text, TRUE);
 #endif
 
-  g_string_append (sparql, ". FILTER (");
+  g_string_append (sparql, ". FILTER (BOUND(nie:url(?urn)) && ");
 
   g_string_append (sparql, "fn:contains(fn:lower-case(nfo:fileName(?urn)),");
   sparql_append_string_literal_lower_case (sparql, search_text);