From bfc1def1d55396268be3fbdb03e117a0610b5d37 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?V=C3=ADtor=20Santos=20Costa?= <vsc@dcc.fc.up.pt>
Date: Tue, 20 Sep 2011 09:54:30 +0100
Subject: [PATCH] imake sure mutable is available.

---
 packages/CLPBN/clpbn.yap | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/packages/CLPBN/clpbn.yap b/packages/CLPBN/clpbn.yap
index 0d8733be9..ef70663b6 100644
--- a/packages/CLPBN/clpbn.yap
+++ b/packages/CLPBN/clpbn.yap
@@ -166,7 +166,8 @@ clpbn_flag(parameter_softening,Before,After) :-
 % we use a mutable variable to avoid unnecessary trailing.
 %
 store_var(El) :- 
-	nb_current(clpbn_qvars, Mutable), !,
+	nb_current(clpbn_qvars, Mutable), 
+	nonvar(Mutable), !,
 	get_mutable(Tail, Mutable),
 	update_mutable(El.Tail, Mutable).
 store_var(El) :-