Oliver Hader authored Oct 09, 2012 and Oliver Hader committed Nov 10, 2012

The current implementation in the TYPO3 backend does not allow
to store NULL values, only empty strings or zero as number are
allowed.
Since the overlay behavior of FAL takes e.g. the description
property from the original file object an empty value in the
disposal (the referenced file) cannot be defined to be blank,
thus not clearing the original file description.

For this case we need a new behavior to allow NULL values in
the storage and to handle that in the backend view.

This feature is enabled by adding "null" to the eval list of
the TCA configuration of a field, example:

'columns' => array(
  'title' => array(
    'config' => array(
      'type' => 'text',
      'eval' => 'null',
    )
  )
)

Besides that, of course the database field definition needs to
be updated to support NULL values.

Change-Id: Ib5cd0e34e34d084df7ba3380ae81e5240bcf76d6
Resolves: #41773
Releases: 6.0
Reviewed-on: http://review.typo3.org/15458
Reviewed-by: Oliver Hader
Tested-by: Oliver Hader