Javascript JS Fetch 数据未定义 promise

我想分析一个从http请求，显示错误，如果需要，然后返回数据.

这就是我现在正在做的事情:

fetch(URL,{method:"GET"})
.then(async response => { await read_errors(response) })
// .then(response => { read_errors(response) }) (Both had been tried)
.then( function(data) { 
    doSomething(data)
})
.catch( error => { display_error(error) })

使用此功能:

async function read_errors(response) {
    const isJson = response.headers.get('content-type')?.includes('application/json');
    const data = isJson ? await response.json() : null;

    const isText = response.headers.get('content-type')?.includes('text/');
    const text = isText ? await response.text() : null;

    // check for error response
    if (!response.ok) {
        // get error message from body or default to response status
        const error = (data && data.message) || text || response.status;
        console.error("Something went wrong : ",error)
        return Promise.reject(error);
    } else {
        fckng_response = isJson ? data : text
        return Promise.resolve(fckng_response)
    }
}

但我有TypeError: data is undefined

来自服务器的答案是正确的，头和数据都是正常的.

我做错了什么？