[server] TypeError: Object false has no method 'setHeader'

[clochix]

Seen in users logs:

TypeError: Object false has no method 'setHeader'
    at Function.Event.byURI (/usr/local/cozy/apps/sync/build/server/models/event.js:122:14)
    at CozyCalDAVBackend.module.exports.CozyCalDAVBackend._findCalendarObject (/usr/local/cozy/apps/sync/build/server/backends/caldav.js:168:23)
    at CozyCalDAVBackend.module.exports.CozyCalDAVBackend.getCalendarObject (/usr/local/cozy/apps/sync/build/server/backends/caldav.js:202:17)
    at Object.module.exports.jsDAV_Collection.extend.getChild (/usr/local/cozy/apps/sync/node_modules/cozy-jsdav-fork/lib/CalDAV/calendar.js:66:28)
    at /usr/local/cozy/apps/sync/node_modules/cozy-jsdav-fork/lib/DAV/objectTree.js:64:24
    at /usr/local/cozy/apps/sync/node_modules/cozy-jsdav-fork/lib/CalDAV/userCalendars.js:126:28
    at /usr/local/cozy/apps/sync/node_modules/cozy-jsdav-fork/lib/CalDAV/userCalendars.js:146:13
    at null._onTimeout (/usr/local/cozy/apps/sync/build/server/backends/caldav.js:80:18)
    at Timer.listOnTimeout [as ontimeout] (timers.js:121:15)