[rygel] rygel: Do not pass null to DBus

[Jens Georg <jensgeorg src gnome org>]

commit b3bfd3c70c527659a30cdc0af86065db69a7a85a
Author: Jens Georg <mail jensge org>
Date:   Thu Mar 31 22:37:12 2016 +0200

    rygel: Do not pass null to DBus
    
    Signed-off-by: Jens Georg <mail jensge org>

 src/rygel/rygel-acl.vala |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/rygel/rygel-acl.vala b/src/rygel/rygel-acl.vala
index 5f5e1a5..7a2c18f 100644
--- a/src/rygel/rygel-acl.vala
+++ b/src/rygel/rygel-acl.vala
@@ -104,7 +104,7 @@ internal class Rygel.Acl : GLib.Object, GUPnP.Acl
                                                      service_hash,
                                                      path,
                                                      address,
-                                                     agent);
+                                                     agent ?? "");
             return allowed;
         } catch (Error error) {
             warning (_("Failed to query ACL: %s"), error.message);