[TD-3914]<fix>: taosdemo input argument validation. (#6097)

Co-authored-by: NShuduo Sang <sdsang@taosdata.com>

src/kit/taosdemo/taosdemo.c

@@ -725,7 +725,6 @@ static void parse_args(int argc, char *argv[], SArguments *arguments) {
         exit(EXIT_FAILURE);
       }
       tstrncpy(configDir, argv[++i], TSDB_FILENAME_LEN);
-
     } else if (strcmp(argv[i], "-h") == 0) {
       if (argc == i+1) {
         printHelp();
@@ -849,6 +848,11 @@ static void parse_args(int argc, char *argv[], SArguments *arguments) {
       }
       arguments->num_of_CPR = atoi(argv[++i]);
     } else if (strcmp(argv[i], "-b") == 0) {
+      if (argc == i+1) {
+        printHelp();
+        errorPrint("%s", "\n\t-b need valid string following!\n");
+        exit(EXIT_FAILURE);
+      }
       sptr = arguments->datatype;
       ++i;
       if (strstr(argv[i], ",") == NULL) {