[api-extractor] Empty declaration in API report for unexported element

[hiranya911]

Summary

We have an unexported interface declaration in one of our namespaces:

export namespace foo {
  interface Bar {
    name: string;
  }

  export interface BarEx extends Bar {
    score: number;
  }
}

This results in the following API report:

// @public (undocumented)
export namespace foo {
    // (undocumented)
    export interface Bar {
        // (undocumented)
        name: string;
    }
    // (undocumented)
    export interface BarEx extends Bar {
        // (undocumented)
        score: number;
    }
        {};
}

Notice the empty {}; line at the end. Exporting the interface Bar makes it go away.

Repro steps

See above.

Standard questions

Please answer these questions to help us investigate your issue more quickly:

Question	Answer
@microsoft/api-extractor version?	v7.18.x
Operating system?	Mac / Linux
API Extractor scenario?	reporting (.api.md)
TypeScript compiler version?	3.9.6
Node.js version (node -v)?	v10 and up