Models with 'additional properties', but no 'properties' produce no output

[aktary]

Given a TypeScript interface:

export interface IManagementFee {
    [symbol: string]: number;
}

... which gets generated into this v2 swagger:

"IManagementFee": {
			"properties": {},
			"type": "object",
			"additionalProperties": {
				"type": "number",
				"format": "double"
			}
		},

the output is:

    export interface IManagementFee {
    }

I would expect the output to be the same as the input.

[lukeautry]

Implemented in v1.3.1