我想写一个合约，该合约可以转移波场shasta的usdt，以下是我代码 1。我用的是波场shasta测试网 2.我使用了官方的代码模板 https://github.com/TRON-Developer-Hub/TRC20-Contract-Template 3。transferuuu的usdt地址是TG3XXyExBkPp9nzdajDZsozEu4BkaSJozs，也就是contractaddress参数值，我执行地址是有usdt的

问题： 我用TRON-IDE部署后，执行transferuuu函数,amount如果是0可以正常执行，但是大于1时，从外部执行，提示错误信息：REVERT opcode executed。请问怎么回事

以下是我TRON-IDE截图

以下是报错截图 以下是我代码

` pragma solidity ^0.5.0;

import "./ITRC20.sol"; import "./SafeMath.sol";

contract TRC20 is ITRC20 {

ITRC20  private _uuuu; 

function transfer(address recipient, uint256 amount) public returns (bool) {
    emit Transfer(msg.sender, recipient, amount);
    // _transfer(msg.sender, recipient, amount);
    return true;
}

 function _transfer(address sender, address recipient, uint256 amount) internal {
    require(sender != address(0), "TRC20: transfer from the zero address");
    require(recipient != address(0), "TRC20: transfer to the zero address");

    _balances[sender] = _balances[sender].sub(amount);
    _balances[recipient] = _balances[recipient].add(amount);
    emit Transfer(sender, recipient, amount);
}

function transferuuu(address contractaddress,address recipient, uint256 amount) public returns (bool) {
     _uuuu = ITRC20(contractaddress);
    _uuuu.transfer(recipient,amount);
    // return true;
}

}`