preproc: Fix out of range access in expand mmacro

On specially crafetd malformed input file the params
might be zapped (say due to invalid syntax) so we might
access out of bound having nil dereference in best case.

Note the later code in this helper uses tok_isnt_ helper
which already has similar check.

https://bugzilla.nasm.us/show_bug.cgi?id=3392518

Reported-by: Jordan Zebor <j.zebor@f5.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>

asm/preproc.c

@@ -3947,6 +3947,8 @@ static Token *expand_mmac_params_range(MMacro *mac, Token *tline, Token ***last)
      * only first token will be passed.
      */
     tm = mac->params[(fst + mac->rotate) % mac->nparam];
+    if (!tm)
+        goto err;
     head = new_Token(NULL, tm->type, tm->text, 0);
     tt = &head->next, tm = tm->next;
     while (tok_isnt_(tm, ",")) {