[TD-4915]<fix> fix show create database except

src/client/src/tscLocal.c

@@ -485,6 +485,7 @@ static int32_t tscGetDBInfo(SCreateBuilder *builder, char *result) {
 
   char buf[TSDB_DB_NAME_LEN + 64] = {0}; 
   do {
+    memset(buf, 0, sizeof(buf));
     int32_t* lengths = taos_fetch_lengths(pSql);  
     int32_t ret = tscGetNthFieldResult(row, fields, lengths, 0, buf);
     if (0 == ret && STR_NOCASE_EQUAL(buf, strlen(buf), builder->buf, strlen(builder->buf))) {