[BUGFIX] Prevent undefined array key error in StoragePermissionsAspect

For not yet migrated filemount records, the
StoragePermissionsAspect previously triggered
an undefined array key since the new field "identifier"
(see #97922) might be empty or at least does not
contain the combined identifier with the ":" sign.

Resolves: #98300
Related: #97922
Releases: main
Change-Id: I17671f6ab785983ed77f3990ec5c353e6d099bc2
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/75664
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Jochen <rothjochen@gmail.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Jochen <rothjochen@gmail.com>
Reviewed-by: Oliver Bartsch <bo@cedev.de>

typo3/sysext/core/Classes/Resource/Security/StoragePermissionsAspect.php

@@ -62,6 +62,10 @@ public function addUserPermissionsToStorage(AfterResourceStorageInitializationEv
     private function addFileMountsToStorage(ResourceStorage $storage)
     {
         foreach ($GLOBALS['BE_USER']->getFileMountRecords() as $fileMountRow) {
+            if (!str_contains($fileMountRow['identifier'], ':')) {
+                // Skip record since the file mount identifier is invalid
+                continue;
+            }
             [$base, $path] = GeneralUtility::trimExplode(':', $fileMountRow['identifier'], false, 2);
             if ((int)$base === (int)$storage->getUid()) {
                 try {