Comment 61 for bug 633352

I'm getting this same situation in Lightning 1.9 in Thunderbird 19 when attempting to dismiss notifications on events created by CalDAV Sync on my Android phone instead of from Lightning. This is against my Owncloud sever (SabreDAV)

This is potentially a simple bug with an easy fix as the error message points out: Line 660 in calDavCalendar.js (in doModifyItem) is assuming the item is in the cache. Maybe it being created elsewhere (as in my phone or the above shared calendar example) causes it not to be there?

let wasInboxItem = this.mItemInfoCache[aNewItem.id].isInboxItem;

Perhaps it's just a matter of checking first? Or does it need to be in mItemInfoCache? Could do something like this:

let wasInboxItem = (typeof this.mItemInfoCache[aNewItem.id] !== 'undefined') && this.mItemInfoCache[aNewItem.id].isInboxItem;