Fix #12702 fuzzing crash in TemplateSimplifier::useDefaultArgumentValues (#6387)

Author: chrchr-github

lib/tokenize.cpp

@@ -8766,6 +8766,8 @@ void Tokenizer::findGarbageCode() const
     // Garbage templates..
     if (isCPP()) {
         for (const Token *tok = tokens(); tok; tok = tok->next()) {
+            if (Token::simpleMatch(tok, "< >") && !(Token::Match(tok->tokAt(-1), "%name%") || (tok->tokAt(-1) && Token::Match(tok->tokAt(-2), "operator %op%"))))
+                syntaxError(tok);
             if (!Token::simpleMatch(tok, "template <"))
                 continue;
             if (tok->previous() && !Token::Match(tok->previous(), ":|;|{|}|)|>|\"C++\"")) {

test/cli/fuzz-crash/crash-adb20a108c3686d79bc9bd0e4025445e3a35fa49.crdownload

@@ -0,0 +1 @@
+template<#p<>tu< <>tu=e