Failure when generating empty union

[tuluce]

What happened?

When we have a union type with no sub-types:

MyEmptyUnion:
  union: {}

The following class is generated:

export type IMyEmptyUnion;

export interface IMyEmptyUnionVisitor<T> {
    'unknown': (obj: IMyEmptyUnion) => T;
}

function visit<T>(obj: IMyEmptyUnion, visitor: IMyEmptyUnionVisitor<T>): T {
    return visitor.unknown(obj);
}

export const IMyEmptyUnion = {
    visit: visit
};

And compileTypeScript step fails with:

myEmptyUnion.ts(1,26): error TS4081: Exported type alias 'IMyEmptyUnion' has or is using private name ''.
myEmptyUnion.ts(1,26): error TS1005: '=' expected.

What did you want to happen?

I'd expect a compilable empty union class, or I'd expect Conjure spec layer to disallow empty unions.

More details

This bug was introduced with the version 5.6.0, looking at the diff 5.5.0...5.6.0, I suspect #247 might have caused it.