Version 1.3.6 Core: * better detection of whether OpenTasks is installed or not (fixes Android 7 phantom sync entries) * automatically enable/disable task sync when OpenTasks is (un)installed * fix "permissions required" notification * update to SDK level 25 (Android 7.1.1) CalDAV: * remove ORGANIZER from all VEVENT components if there are not attendees CardDAV: * update to ez-vcard/0.10.1 * improve parsing of uncommon REV/timestamp formats (fixes current Nextcloud/OwnCloud Contacts problems) * ignore invalid PREF values