[BUGFIX] Fix PHP 8 warning in TreeDataProvider

Resolves: #99315
Releases: main, 11.5
Change-Id: Ib6bae3be83742212d063bd7b746bb2885d79222b
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/77572


Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>

typo3/sysext/core/Classes/Tree/TableConfiguration/DatabaseTreeDataProvider.php

@@ -508,7 +508,7 @@ class DatabaseTreeDataProvider extends AbstractTableConfigurationTreeDataProvide
                 // Intentional fall-through
             case 'select':
             case 'category':
-                if ($this->columnConfiguration['MM']) {
+                if ($this->columnConfiguration['MM'] ?? false) {
                     $dbGroup = GeneralUtility::makeInstance(RelationHandler::class);
                     $dbGroup->start(
                         $value,
@@ -519,7 +519,7 @@ class DatabaseTreeDataProvider extends AbstractTableConfigurationTreeDataProvide
                         $this->columnConfiguration
                     );
                     $relatedUids = $dbGroup->tableArray[$this->getTableName()];
-                } elseif ($this->columnConfiguration['foreign_field']) {
+                } elseif ($this->columnConfiguration['foreign_field'] ?? false) {
                     $queryBuilder = GeneralUtility::makeInstance(ConnectionPool::class)
                         ->getQueryBuilderForTable($this->getTableName());
                     $queryBuilder->getRestrictions()->removeAll();