[glib] gdbusauth: fix crash when server data send returns NULL

[Ignacio Casal Quinteiro <icq src gnome org>]

commit 463a8636059864c3120f496bfd578fb65e998394
Author: Ignacio Casal Quinteiro <icq gnome org>
Date:   Tue Nov 29 13:12:47 2016 +0100

    gdbusauth: fix crash when server data send returns NULL
    
    _g_dbus_auth_mechanism_server_data_send may fail in which case
    we would endup getting a NULL data. In this case we should not
    try to encode the data and simply let the state machine to continue.
    The auth mechanism will change internally to REJECTED so we just
    need to continue the iteration.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=775309

 gio/gdbusauth.c |   24 +++++++++++++++---------
 1 files changed, 15 insertions(+), 9 deletions(-)
---
diff --git a/gio/gdbusauth.c b/gio/gdbusauth.c
index 4036d77..a870e86 100644
--- a/gio/gdbusauth.c
+++ b/gio/gdbusauth.c
@@ -1207,19 +1207,25 @@ _g_dbus_auth_run_server (GDBusAuth              *auth,
                       {
                         gchar *data;
                         gsize data_len;
-                        gchar *encoded_data;
+
                         data = _g_dbus_auth_mechanism_server_data_send (mech, &data_len);
-                        encoded_data = hexencode (data);
-                        s = g_strdup_printf ("DATA %s\r\n", encoded_data);
-                        g_free (encoded_data);
-                        g_free (data);
-                        debug_print ("SERVER: writing '%s'", s);
-                        if (!g_data_output_stream_put_string (dos, s, cancellable, error))
+                        if (data != NULL)
                           {
+                            gchar *encoded_data;
+
+                            encoded_data = hexencode (data);
+                            s = g_strdup_printf ("DATA %s\r\n", encoded_data);
+                            g_free (encoded_data);
+                            g_free (data);
+
+                            debug_print ("SERVER: writing '%s'", s);
+                            if (!g_data_output_stream_put_string (dos, s, cancellable, error))
+                              {
+                                g_free (s);
+                                goto out;
+                              }
                             g_free (s);
-                            goto out;
                           }
-                        g_free (s);
                       }
                       goto change_state;
                       break;