[BUGIFX] File Reference cannot be used to disable specific meta data

The meta data (like description, title, ...) in File References
cannot be used to disable the inherited data from the parent
File object. Currently values can be blank which results in
using data from the parent. To really override by using blanks,
the new NULL feature for TCA fields needs to be used.

Change-Id: I61e5f5e6a0d848e95e2e0402913778ef9f63a093
Fixes: #43132
Releases: 6.0
Reviewed-on: http://review.typo3.org/16602
Reviewed-by: Helmut Hummel
Tested-by: Helmut Hummel

t3lib/stddb/tca_sys_file_reference.php

@@ -133,6 +133,7 @@ $TCA['sys_file_reference'] = array(
 			'label' => 'LLL:EXT:lang/locallang_tca.xlf:sys_file_reference.title',
 			'config' => array(
 				'type' => 'input',
+				'eval' => 'null',
 				'size' => '22',
 				'placeholder' => '__row|uid_local|title'
 			)
@@ -163,6 +164,7 @@ $TCA['sys_file_reference'] = array(
 			'label' => 'LLL:EXT:lang/locallang_tca.xlf:sys_file_reference.description',
 			'config' => array(
 				'type' => 'text',
+				'eval' => 'null',
 				'cols' => '24',
 				'rows' => '5'
 			)
@@ -173,6 +175,7 @@ $TCA['sys_file_reference'] = array(
 			'label' => 'LLL:EXT:lang/locallang_tca.xlf:sys_file_reference.alternative',
 			'config' => array(
 				'type' => 'input',
+				'eval' => 'null',
 				'size' => '22',
 				'placeholder' => '__row|uid_local|alternative'
 			),