cypress.request is inserting null into the request url.

A null is being injected into the request url.
## Cypress.json

```
{
  baseUrl: 'http://localhost:3003/'
}
```
## Test code

```
cypress.request('POST', 'v2/some/url', {name: 'jane'})
```
## Resulting request

```
POST  http://localhost:3003/null/v2/some/url
```
