From d81a13804094f7f8cffd83511bdde28bb91909eb Mon Sep 17 00:00:00 2001
From: Cas Cremers <cas.cremers@gmail.com>
Date: Mon, 24 Dec 2018 14:10:30 +0100
Subject: [PATCH] Safety: added assert.

---
 src/mgu.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/mgu.c b/src/mgu.c
index ad702dc..c28cc61 100644
--- a/src/mgu.c
+++ b/src/mgu.c
@@ -19,6 +19,7 @@
 
 #include <stdlib.h>
 #include <stdio.h>
+#include <assert.h>
 #include "term.h"
 #include "termlist.h"
 #include "mgu.h"
@@ -140,6 +141,7 @@ unify_callback_wrapper (Termlist tl, struct state_mgu_tmp *ptr_tmpstate)
 {
   // now the keys are unified (subst in this tl)
   // and we try the inner terms
+  assert (ptr_tmpstate != NULL);
   return unify (ptr_tmpstate->unifyt1, ptr_tmpstate->unifyt2, tl,
 		ptr_tmpstate->oldcallback, ptr_tmpstate->oldstate);
 }