Correctly process email tickets for existing users

If a ticket is created via email for an existing user, under some
circumstances, no user will be associated with the new ticket.
Merge pull request #588 from greezybacon/issue/526

Correctly process email tickets for existing users

Reviewed-By: @rougeAU
Reviewed-By: @syscom2
Reviewed-By: @centoasa
Reviewed-By: @vhadjisophocle