Empty schemas generate invalid code

[seanlaff]

responses:
        "204":
          description: pet deleted
          content:
            application/json:
              schema:
                properties: {}

Will generated a type that looks like

export interface PetDeleteResponse {
;
}

The getObject() function builds an array, joins it with ;\n, and then appends ;. The bug being that the trailing ; gets appended even if the array was empty.