change_profile's target namespace parsing doesn't work as intended

While modifying the change_profile rule parsing logic, I noticed that the
portion that is intended to parse the target profile's namespace is not working
as intended:

parser/parser_yacc.y:
  1525 change_profile: change_profile_head TOK_ARROW opt_ns TOK_ID TOK_END_OF_RULE
  1526 {
  1527 struct cod_entry *entry;
  1528 PDEBUG("Matched change_profile: tok_id (:%s://%s)\n", $3 ? $3 : "", $4);
  1529 entry = new_entry($3, $4, AA_CHANGE_PROFILE, $1);
  1530 if (!entry)
  1531 yyerror(_("Memory allocation error."));
  1532 PDEBUG("change_profile.entry: (%s)\n", entry->name);
  1533 $$ = entry;
  1534 };

$ echo "/t { change_profile /bin/true -> :ns://profile, }" | ./parser/apparmor_parser -qQ
...
parser: Matched change_profile: tok_id (:://:ns://profile)
...

You can see from the PDEBUG() output that NULL is being passed as the first
parameter to new_entry(). I've also verified this through other means.