Avoid a potential buffer overrun if an SQL statement being parsed ends

with an illegal "!" token.  (This problem was detected by fuzzcheck
running under valgrind. The problem was introduced by check-in [9570b6b43df3].)

FossilOrigin-Name: 2a8d97e7c8976df0312e1294e8c1da8b15686654

src/tokenize.c

@@ -285,7 +285,7 @@ int sqlite3GetToken(const unsigned char *z, int *tokenType){
     case CC_BANG: {
       if( z[1]!='=' ){
         *tokenType = TK_ILLEGAL;
-        return 2;
+        return 1;
       }else{
         *tokenType = TK_NE;
         return 2;