[BUGFIX] Prevent exception for invalid file link

Using an invalid uid to link to a file
does no longer throw an exception, since
this prevents the backend user from fixing
the invalid entry, because the edit form
can no longer be accessed.

Resolves: #102670
Releases: main, 12.4
Change-Id: I634eb88a2ddf671abbb88870d664e739e8127ce9
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/82201


Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Jochen Roth <rothjochen@gmail.com>
Reviewed-by: Jochen Roth <rothjochen@gmail.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Benni Mack <benni@typo3.org>

typo3/sysext/core/Classes/LinkHandling/FileLinkHandler.php

@@ -86,10 +86,10 @@ class FileLinkHandler implements LinkHandlingInterface
      */
     protected function resolveFile(array $data): ?FileInterface
     {
-        if (isset($data['uid'])) {
+        if (is_numeric($data['uid'] ?? false)) {
             return $this->getResourceFactory()->getFileObject($data['uid']);
         }
-        if (isset($data['identifier'])) {
+        if (is_string($data['identifier'] ?? false) && $data['identifier'] !== '') {
             return $this->getResourceFactory()->getFileObjectFromCombinedIdentifier($data['identifier']);
         }
         return null;