storeURL: policy error: proper credentials were not provided

Starting from version 1.13.0 it seems that storeURL generates invalid request URL, missing signature and policy which results in error `application [applicationId] policy error: proper credentials were not provided: (signature: ""; policy "")`.

Request URL looks as `https://cdn.filestackcontent.com/[applicationId]/store=filename:collaboration/%22https://example.com/image.png%22`.