No host causes requests to set JWT

[driverpt]

When making HTTP Request without Host, with whitelistedDomains set, it causes JWT Authorization to be set.

If we're using redirect to an S3 Assets Bucket, it causes the Authorization Header to be sent and AWS S3 will reject that, since it doesn't know it.

Prerequisites

• [ x ] I have checked the README documentation.
• [ x ] I have checked the Auth0 Community for related posts.
• [ x ] I have checked for related or duplicate [Issues](https://github.com/auth0/angular2-jwt
  /issues) and [PRs](https://github.com/auth0/angular2-jwt
  /pulls).
• [ x ] I have read the Auth0 general contribution guidelines.
• [ x ] I have read the Auth0 Code of Conduct.
• [ x ] I am reporting this to the correct repository.

Environment

Please provide the following:

@auth0/angular-jwt@2.1.0 on Angular 7

Reproduction

When using ngx-markdown and [src]="/assets/foo/bar.md", the requests are intercepted by the JWT Interceptor but since requestUrl.host is null, cause the JWT Authorization header to be set.
Since we're using AWS ALB to redirect that to another sub-domain (S3 Backed), when Authorization is set, causes the requests to fail (since the Authorization isn't AWS Compatible)