[BUGFIX] FAL: Initialize all NOT NULL fields for new metadata records

[BUGFIX] FAL: Initialize all NOT NULL fields for new metadata records

The columns l10n_diffsource is defined as NOT NULL in the database
schema. When a new record is being created through the method
createMetaDataRecord() this field is not being set, causing errors when
running in MySQL strict mode.

Resolves: #69071
Releases: master
Change-Id: Ie0465abc90c9855c84c8c9bb1c59909316c8dc2e
Reviewed-on: http://review.typo3.org/42629
Reviewed-by: Frans Saris <franssaris@gmail.com>
Reviewed-by: Daniel Goerz <ervaude@gmail.com>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>