[libmanette] device: Simplify *_set_mapping()

[Adrien Plazas <aplazas src gnome org>]

commit c8a16c124a29652013cc323bd411f293d8946d24
Author: Adrien Plazas <kekun plazas laposte net>
Date:   Tue Nov 17 22:36:17 2020 +0100

    device: Simplify *_set_mapping()

 src/manette-device.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)
---
diff --git a/src/manette-device.c b/src/manette-device.c
index 69b4bef..6f0e8d2 100644
--- a/src/manette-device.c
+++ b/src/manette-device.c
@@ -746,10 +746,7 @@ manette_device_set_mapping (ManetteDevice  *self,
 {
   g_return_if_fail (MANETTE_IS_DEVICE (self));
 
-  if (self->mapping != NULL)
-    g_object_unref (self->mapping);
-
-  self->mapping = mapping ? g_object_ref (mapping) : NULL;
+  g_set_object (&self->mapping, mapping);
 }
 
 /**