[BUGFIX] Initialize new session with empty data field

Initialize the ses_data key with an empty string when
creating a new session record to avoid problems with
active MySQL strict mode.

Resolves: #52358
Releases: master
Change-Id: Ib432812797015511aa1b1230eec9d0cc4d391c74
Reviewed-on: http://review.typo3.org/41758


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>
Tested-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>