[TD-4902] FIX -m parameter of taosdemo with letter-initial string (#6620)

* [TD-4902] FIX with 1 char

* Fix prompt of -m @ taosdemo

src/kit/taosdemo/taosdemo.c

@@ -982,9 +982,9 @@ static void parse_args(int argc, char *argv[], SArguments *arguments) {
       arguments->len_of_binary = atoi(argv[++i]);
     } else if (strcmp(argv[i], "-m") == 0) {
       if ((argc == i+1) ||
-        (!isStringNumber(argv[i+1]))) {
+        (isStringNumber(argv[i+1]))) {
         printHelp();
-        errorPrint("%s", "\n\t-m need a number following!\n");
+        errorPrint("%s", "\n\t-m need a letter-initial string following!\n");
         exit(EXIT_FAILURE);
       }
       arguments->tb_prefix = argv[++i];