[gtk+/portal] Report more errors

[Matthias Clasen <matthiasc src gnome org>]

commit 6b00fffbe1a54018b10faae484a7e614b2a89534
Author: Matthias Clasen <mclasen redhat com>
Date:   Wed Jul 6 23:13:23 2016 -0400

    Report more errors
    
    When the PreparePrint call returns an error, propagate that
    up as well.

 gtk/gtkprintoperation-portal.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/gtk/gtkprintoperation-portal.c b/gtk/gtkprintoperation-portal.c
index 4afabd2..b8698b7 100644
--- a/gtk/gtkprintoperation-portal.c
+++ b/gtk/gtkprintoperation-portal.c
@@ -433,7 +433,8 @@ prepare_print_called (GObject      *source,
   ret = g_dbus_proxy_call_finish (portal->proxy, result, &error);
   if (ret == NULL)
     {
-      g_warning ("Error: %s", error->message);
+      if (portal->op->priv->error == NULL)
+        portal->op->priv->error = g_error_copy (error);
       g_error_free (error);
       if (portal->loop)
         g_main_loop_quit (portal->loop);