Fix internal CFI nav logic function
Fix internal CFI nav logic function

Return null instead of an array with an empty object. This is to match the behaviour before the recent refactoring

NYPL-Simplified/readium-shared-js,NYPL-Simplified/readium-shared-js,readium/readium-shared-js,NYPL/readium-shared-js,NYPL/readium-shared-js,readium/readium-shared-js