IMipPlugin check email address earlier

[PVince81]

Steps

1. Enable calendar app
2. Create a new event
3. Add an attendee and use "user2" as email address (at first I thought I could specify a direct user id of OC before finding out that only email addresses work)
4. Create event

Expected

Event created or error message.

Actual

Nothing displayed, dialog closes. No error message.
Exception (from Sentry):

ErrorException: Undefined offset: 1
#23 /srv/www/htdocs/owncloudtest/lib/private/Mail/Message.php(59): handleError
#22 /srv/www/htdocs/owncloudtest/lib/private/Mail/Message.php(59): convertAddresses
#21 /srv/www/htdocs/owncloudtest/lib/private/Mail/Message.php(125): setTo
#20 dav/lib/CalDAV/Schedule/IMipPlugin.php(124): schedule
#19 dav/lib/CalDAV/Schedule/IMipPlugin.php(0): call_user_func_array
#18 /srv/www/htdocs/owncloudtest/lib/composer/sabre/event/lib/EventEmitterTrait.php(105): emit
#17 /srv/www/htdocs/owncloudtest/lib/composer/sabre/dav/lib/CalDAV/Schedule/Plugin.php(384): deliver
#16 /srv/www/htdocs/owncloudtest/lib/composer/sabre/dav/lib/CalDAV/Schedule/Plugin.php(665): processICalendarChange
#15 /srv/www/htdocs/owncloudtest/lib/composer/sabre/dav/lib/CalDAV/Schedule/Plugin.php(367): calendarObjectChange
#14 /srv/www/htdocs/owncloudtest/lib/composer/sabre/dav/lib/CalDAV/Schedule/Plugin.php(0): call_user_func_array
#13 /srv/www/htdocs/owncloudtest/lib/composer/sabre/event/lib/EventEmitterTrait.php(105): emit
#12 /srv/www/htdocs/owncloudtest/lib/composer/sabre/dav/lib/CalDAV/Plugin.php(943): validateICalendar
#11 /srv/www/htdocs/owncloudtest/lib/composer/sabre/dav/lib/CalDAV/Plugin.php(801): beforeCreateFile
#10 /srv/www/htdocs/owncloudtest/lib/composer/sabre/dav/lib/CalDAV/Plugin.php(0): call_user_func_array
#9 /srv/www/htdocs/owncloudtest/lib/composer/sabre/event/lib/EventEmitterTrait.php(105): emit
#8 /srv/www/htdocs/owncloudtest/lib/composer/sabre/dav/lib/DAV/Server.php(1093): createFile
#7 /srv/www/htdocs/owncloudtest/lib/composer/sabre/dav/lib/DAV/CorePlugin.php(525): httpPut
#6 /srv/www/htdocs/owncloudtest/lib/composer/sabre/dav/lib/DAV/CorePlugin.php(0): call_user_func_array
#5 /srv/www/htdocs/owncloudtest/lib/composer/sabre/event/lib/EventEmitterTrait.php(105): emit
#4 /srv/www/htdocs/owncloudtest/lib/composer/sabre/dav/lib/DAV/Server.php(479): invokeMethod
#3 /srv/www/htdocs/owncloudtest/lib/composer/sabre/dav/lib/DAV/Server.php(254): exec
#2 dav/lib/Server.php(298): exec
#1 dav/appinfo/v2/remote.php(31): require_once
#0 /srv/www/htdocs/owncloudtest/remote.php(165): null

Version

ownCloud 10.0.10 RC2

@DeepDiver1975 FYI

[ownclouders]

GitMate.io thinks possibly related issues are #16057 (Not possible to remove email address from personal info), #24820 (bcc multiple email addresses ), #6303 (lostpassword and email sharing address issue), and #31741 (Setup page for stable10 / 10.0.9beta broken, chicken-egg problem).

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 10 days if no further activity occurs. Thank you for your contributions.