TYPO3 Core

When I create a page with a normal content element text & images and save the page in a live workspace and then change into a preparation workspace and edit and save the same element everything is fine.
When I create a news element in live workspace and then switch to preparation workspace try to do some changes and save the record I get the error messages:

2: SQL error: 'Incorrect integer value: '' for column 'relatedpublications' at row 1' (tx_news_domain_model_news:NEW5a0c49ebcadee280211182)
1: [newlog()] Could not be edited in offline workspace in the branch where found (failure state: 'Online record was not in versionized branch!'). Auto-creation of version failed!

In this case there is no record created for the news.
If I create a new news element in the preparation workspace without an existing element in live workspace, everything is fine. Both records live and preparation are created and have the correct data.
So when creating the record first in live workspace and then creating a workspace copy of this record the error message turns up. The field relatedpublications is configured like:

    'relatedpublications' => [
        'exclude' => 1,
        'l10n_mode' => '',
        'l10n_display' => 'hideDiff',
        'label' => 'LLL:EXT:mediawall/Resources/Private/Language/locallang_db.xlf:news.relatedpublications',
        'config' => [
            'type' => 'inline',
            'foreign_table' => 'tx_news_domain_model_news',
            'MM_match_fields' => [
                'fieldname' => 'relatedpublications',
            ],
            'foreign_record_defaults' => [
                'hidden' => '0',
                'is_downloadable_news' => '1',
            ],
            'maxitems' => 100,
            'MM' => 'tx_news_domain_model_news_relatedmediawallitem_mm',
            'appearance' => [
                'showSynchronizationLink' => 1,
                'showAllLocalizationLink' => 1,
                'showPossibleLocalizationRecords' => 1,
                'showRemovedLocalizationRecords' => 1,
                'expandSingle' => 1,
                'collapseAll' => 1,
                'newRecordLinkTitle' => 'LLL:EXT:mediawall/Resources/Private/Language/locallang_db.xlf:news.create_new_relatedpublications',
                'enabledControls' => [
                    'info' => true,
                    'new' => true,
                    'dragdrop' => true,
                    'sort' => true,
                    'hide' => true,
                    'delete' => true,
                    'localize' => true,
                ],
            ],
            'behaviour' => [
                'localizationMode' => 'select',
                'localizeChildrenAtParentLocalization' => true,
            ],
            'mediawallitem' => true,
        ],
    ],

This seems correct to me.

In /CMS/Core/DataHanling/DataHandler.php function copyRecord_raw() in line 3762 the field value of relatedpublications is set to an empty string (“”) which in further case produces the errors above.

But when I debug the same with a default content element as text & media the same line has an empty string for the field media which is equal in type as relatedpublication and does not produce an error.