Update tokenize.cpp

Author: chrchr-github

lib/tokenize.cpp

@@ -9550,6 +9550,8 @@ void Tokenizer::simplifyCPPAttribute()
                 Token* head = skipCPPOrAlignAttribute(tok)->next();
                 while (isCPPAttribute(head) || isAlignAttribute(head))
                     head = skipCPPOrAlignAttribute(head)->next();
+                if (!head)
+                    syntaxError(tok);
                 head->isAttributeUnused(true);
             } else if (Token::Match(tok->previous(), ") [ [ expects|ensures|assert default|audit|axiom| : %name% <|<=|>|>= %num% ] ]")) {
                 const Token *vartok = tok->tokAt(4);