fix: ensure file names are string-typed

[blizzz]

• $child was used as an array key earlier. If they are numeric, they are automatically converted to ints, leading to type issues later.

Summary

Fixes an Argument #1 ($haystack) must be of type string, int given on occ files:scan with remotely shared file/folder names that are numbers.

TypeError: str_starts_with(): Argument #1 ($haystack) must be of type string, int given in /var/www/nextcloud/lib/private/Files/Cache/Propagator.php:48
Stack trace:
#0 /var/www/nextcloud/lib/private/Files/Cache/Propagator.php(48): str_starts_with()
#1 /var/www/nextcloud/lib/private/Files/Utils/Scanner.php(290): OC\Files\Cache\Propagator->propagateChange()
#2 /var/www/nextcloud/lib/private/Files/Utils/Scanner.php(294): OC\Files\Utils\Scanner->triggerPropagator()
#3 /var/www/nextcloud/lib/private/Files/Utils/Scanner.php(238): OC\Files\Utils\Scanner->postProcessEntry()
#4 [internal function]: OC\Files\Utils\Scanner->OC\Files\Utils\{closure}()
#5 /var/www/nextcloud/lib/private/Hooks/EmitterTrait.php(89): call_user_func_array()
#6 /var/www/nextcloud/lib/private/Files/Cache/Scanner.php(253): OC\Hooks\BasicEmitter->emit()
#7 /var/www/nextcloud/lib/private/Files/Cache/Scanner.php(530): OC\Files\Cache\Scanner->removeFromCache()
#8 /var/www/nextcloud/lib/private/Files/Cache/Scanner.php(414): OC\Files\Cache\Scanner->handleChildren()
#9 /var/www/nextcloud/lib/private/Files/Cache/Scanner.php(323): OC\Files\Cache\Scanner->scanChildren()
#10 /var/www/nextcloud/apps/files_sharing/lib/External/Scanner.php(22): OC\Files\Cache\Scanner->scan()
#11 /var/www/nextcloud/lib/private/Files/Utils/Scanner.php(265): OCA\Files_Sharing\External\Scanner->scan()
#12 /var/www/nextcloud/apps/files/lib/Command/Scan.php(165): OC\Files\Utils\Scanner->scan()
#13 /var/www/nextcloud/apps/files/lib/Command/Scan.php(255): OCA\Files\Command\Scan->scanFiles()
#14 /var/www/nextcloud/3rdparty/symfony/console/Command/Command.php(326): OCA\Files\Command\Scan->execute()
#15 /var/www/nextcloud/core/Command/Base.php(218): Symfony\Component\Console\Command\Command->run()
#16 /var/www/nextcloud/3rdparty/symfony/console/Application.php(1083): OC\Core\Command\Base->run()
#17 /var/www/nextcloud/3rdparty/symfony/console/Application.php(324): Symfony\Component\Console\Application->doRunCommand()
#18 /var/www/nextcloud/3rdparty/symfony/console/Application.php(175): Symfony\Component\Console\Application->doRun()
#19 /var/www/nextcloud/lib/private/Console/Application.php(187): Symfony\Component\Console\Application->run()
#20 /var/www/nextcloud/console.php(90): OC\Console\Application->run()
#21 /var/www/nextcloud/occ(33): require_once('...')
#22 {main}

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

AI (if applicable)

• The content of this PR was partly or fully generated using AI

[blizzz]

/backport to stable34

[blizzz]

/backport to stable33

[blizzz]

/backport to stable32