[gnome-settings-daemon] wacom: Fix NULL pointer dereference

[Bastien Nocera <hadess src gnome org>]

commit 617fe8512cfb3e5491785b4375785f08c8996a84
Author: Jason Gerecke <killertofu gmail com>
Date:   Mon Jan 23 15:37:30 2012 -0800

    wacom: Fix NULL pointer dereference
    
    If the public gsd_wacom_device_get_display_monitor function is
    called, it eventually finds its way up here. With a NULL 'device'
    argument, we segfault rather than gracefully returning NULL as
    other exceptional conditions in the function do.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=668545

 plugins/wacom/gsd-wacom-device.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/plugins/wacom/gsd-wacom-device.c b/plugins/wacom/gsd-wacom-device.c
index 062e0cf..04b5305 100644
--- a/plugins/wacom/gsd-wacom-device.c
+++ b/plugins/wacom/gsd-wacom-device.c
@@ -480,6 +480,9 @@ find_output_by_display (GsdWacomDevice *device)
 	GVariant *display;
 	const gchar **edid;
 
+	if (device == NULL)
+		return NULL;
+
 	tablet   = device->priv->wacom_settings;
 	display  = g_settings_get_value (tablet, "display");
 	edid     = g_variant_get_strv (display, &n);