C2 : A message without title will generate a notification but we will loose the content

[NicoDucou]

When creating a new message, the title field is circled in red to see that it is required, but if we send the message without putting a title it gets back to the message list (inbox) and we have a red message indicating an error "Submit validation failed" but we loose the message we had written.
We should not be able to click the send button or at least it should do nothing if the title is not set

Same thing if there is no user to send the message to defined. Because for the moment it goes back to the inbox and show a red message indicating
"Handling "Chamilo\CoreBundle\Entity\Message" failed: Handling "Symfony\Component\Mailer\Messenger\SendEmailMessage" failed: An email must have a "To", "Cc", or "Bcc" header."