TypeError [ERR_HTTP_INVALID_HEADER_VALUE]: Invalid value "undefined" for header "Content-Length"

Hello. When I use unirest to make a request a get an error ' Invalid value "undefined" for header "Content-Length" '. How can I prevent that? It happens from time to time, but not every time. I'm using node.js on backend for my application. Here is my function

```
function addTasks(object) {
return new Promise((resolve, reject) => {
unirest.post(`${xtmBaseUrl}/rest-api/projects`)
.headers({"Authorization": xtmToken,
'Content-Type': 'multipart/form-data'})
.field('customerId', object.customerId)
.field('name', object.name)
.field('sourceLanguage', object.source)
.field('targetLanguages', object.target)
.field('analysisTemplateId', object.templateId)
.field(withJoinObject)
.attach(filesObj)
.end(response => {
if(response.error) {
reject(response.error)
}
resolve(response.body)
})
})
}
```

Start with the addTasks function and trace the unirest.post multipart request built with headers, fields, and attachments. Reproduce the intermittent failure and inspect how the request reaches the Content-Length header; done means the same request no longer produces an undefined header value and the intermittent path is covered or explained.

Written by the indexing model from the issue text.