Undefine indexes in sessions after 2.1.3 upgrade

[eluser]GreGre[/eluser]
I get the following notices in my logs after upgrade to 2.1.3

Code:

ERROR - 2012-12-04 00:21:54 --> Severity: Notice  --> Undefined index: session_id  [system_path]/libraries/Session.php 272
ERROR - 2012-12-04 00:21:54 --> Severity: Notice  --> Undefined index: ip_address [system_path]/libraries/Session.php 272
ERROR - 2012-12-04 00:21:54 --> Severity: Notice  --> Undefined index: user_agent [system_path]libraries/Session.php 272
ERROR - 2012-12-04 00:21:54 --> Severity: Notice  --> Undefined index: last_activity [system_path]
/libraries/Session.php 272

I know it's probably no big deal, but I like my code clean and my logs unspamed. Sometime notices are important and sessions are the critical point for the safety of a script.

Is it a new bug or anything else?

Regards, Gregor