pageIndex -1 degrade gracefully to 0 (to avoid blank viewport), see https://github.com/readium/readium-shared-js/issues/260
pageIndex -1 degrade gracefully to 0 (to avoid blank viewport), see
https://github.com/readium/readium-shared-js/issues/260

NYPL-Simplified/readium-shared-js,NYPL/readium-shared-js,ravn-no/readium-shared-js,kivuto/readium-shared-js,NYPL/readium-shared-js,kivuto/readium-shared-js,readium/readium-shared-js,NYPL-Simplified/readium-shared-js,JoMedia/readium-shared-js,readium/readium-shared-js,ravn-no/readium-shared-js