[mutter] backend: simplify assert

[Jonas Ådahl <jadahl src gnome org>]

commit 125cba71002443cd3a227815b408d6b875a58f93
Author: Thomas Hindoe Paaboel Andersen <phomes gmail com>
Date:   Thu Jul 21 21:12:16 2016 +0200

    backend: simplify assert
    
    We already checked that constraint is non-null.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=769054

 src/backends/meta-backend.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/backends/meta-backend.c b/src/backends/meta-backend.c
index 2fbedcb..e5a09de 100644
--- a/src/backends/meta-backend.c
+++ b/src/backends/meta-backend.c
@@ -615,7 +615,7 @@ void
 meta_backend_set_client_pointer_constraint (MetaBackend           *backend,
                                             MetaPointerConstraint *constraint)
 {
-  g_assert (!constraint || (constraint && !backend->client_pointer_constraint));
+  g_assert (!constraint || !backend->client_pointer_constraint);
 
   g_clear_object (&backend->client_pointer_constraint);
   if (constraint)