When device_state notif mailer is called, empty users email field causes stacktrace in server logs

[andrey-utkin]

I(1/name): Making a snapshot
I(1/name): Saved snapshot from single keyframe
PHP Fatal error:  Uncaught Swift_RfcComplianceException: Address in mailbox given [] does not comply with RFC 2822, 3.6.2. in /usr/share/bluecherry/www/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Mime/Headers/MailboxHeader.php:355
Stack trace:
#0 /usr/share/bluecherry/www/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Mime/Headers/MailboxHeader.php(272): Swift_Mime_Headers_MailboxHeader->assertValidAddress()
#1 /usr/share/bluecherry/www/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Mime/Headers/MailboxHeader.php(117): Swift_Mime_Headers_MailboxHeader->normalizeMailboxes()
#2 /usr/share/bluecherry/www/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Mime/Headers/MailboxHeader.php(74): Swift_Mime_Headers_MailboxHeader->setNameAddresses()
#3 /usr/share/bluecherry/www/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Mime/SimpleHeaderFactory.php(61): Swift_Mime_Headers_MailboxHeader->setFieldBodyModel()
#4 /usr/share/bluecherry/www/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Mime/SimpleHeaderSet.php(71): Swift_Mime_SimpleHeaderFactory->createMailboxHeader()
#5 /usr/share/bluecherry/www/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Mime/SimpleMessage.php(323): Swift_Mime_SimpleHeaderSet->addMailboxHeader()
#6 /usr/share/bluecherry/www/lib/mailer.php(314): Swift_Mime_SimpleMessage->setTo()
#7 {main}
  thrown in /usr/share/bluecherry/www/vendor/swiftmailer/swiftmailer/lib/classes/Swift/Mime/Headers/MailboxHeader.php on line 355