mes: assq, assoc-ref: Handle non-A-LISTs.

* src/mes.c (assq): Return #f if A-LIST is not a list.
* module/mes/scm.mes (assoc): Likewise.

module/mes/scm.mes

@@ -109,7 +109,7 @@
 (define assv-ref assq-ref)
 
 (define (assoc key alist)
-  (if (null? alist) #f
+  (if (not (pair? alist)) #f
       (if (equal? key (caar alist)) (car alist)
           (assoc key (cdr alist)))))
 

src/mes.c

@@ -713,6 +713,8 @@ call (SCM fn, SCM x)
 SCM
 assq (SCM x, SCM a)
 {
+  if (TYPE (a) != TPAIR)
+    return cell_f;
   switch (TYPE (x))
     {
     case TCHAR: