[User] Do not try to alias if user is the same

Signed-off-by: Miguel M. Almeida <miguelcma@gmail.com>
[User] Fix infinite loop at identifyUserWithIdentifier:alias:

Signed-off-by: Miguel M. Almeida <miguelcma@gmail.com>
[Event] Avoid data points without user or session

Signed-off-by: Miguel M. Almeida <miguelcma@gmail.com>