Fix #12701 fuzzing crash in Tokenizer::findGarbageCode() (#6378)

Author: chrchr-github

lib/tokenize.cpp

@@ -5533,6 +5533,8 @@ bool Tokenizer::simplifyTokenList1(const char FileName[])
     // remove __attribute__((?))
     simplifyAttribute();
 
+    validate();
+
     // Bail out if code is garbage
     if (mTimerResults) {
         Timer t("Tokenizer::simplifyTokens1::simplifyTokenList1::findGarbageCode", mSettings.showtime, mTimerResults);

test/cli/fuzz-crash/crash-cb1d71440b24712fdf0bdcee43b9b3f1bc35c0d0

@@ -0,0 +1 @@
+(n@()###);