[Bug]: maintenance:repair --include-expensive crashes in CleanupShareTarget: Call to a member function getRootId() on null #63494

Bug description

While running the repair steps after upgrading to 34.0.3, occ maintenance:repair --include-expensive aborts at the new "Cleanup share names with false conflicts" step:

 - Cleanup share names with false conflicts
  28/907 [>---------------------------]   3%An unhandled exception has been thrown:
Error: Call to a member function getRootId() on null in apps/files_sharing/lib/Repair/CleanupShareTarget.php:128

Root cause (apps/files_sharing/lib/Repair/CleanupShareTarget.php):

$oldMountPoint = "/{$recipient->getUID()}/files$oldTarget/";
...
/** @var ICachedMountInfo $mount */
$mount = $userMounts[$oldMountPoint];        // line 122 — no null check
...
'fileid' => $mount->getRootId(),             // line 128 — fatals when the key is missing

$userMounts is built from IUserMountCache::getMountsForUser(). When the recipient's mount cache has no entry for the old share target (in our case some recipients hadn't logged in for a long time, so oc_mounts had no row for those targets), the array lookup yields null and the getRootId() call throws Error.

Two aggravating details:

1. Line 111 in the same method already guards the exact same lookup with fn ($path) => $userMounts[$path] ?? null — line 122 just misses the same guard.
2. The catch (\Exception $e) at line 132 doesn't catch \Error, so the whole repair run aborts instead of skipping the one share.

Note that moveShare() (line 116) has already updated the oc_share row at that point — only the mount-cache refresh needs guarding, and the cache rebuilds itself on the user's next login anyway.

Suggested fix:

/** @var ICachedMountInfo|null $mount */
$mount = $userMounts[$oldMountPoint] ?? null;
if ($mount !== null) {
    $userMounts[$newMountPoint] = $mount;
    unset($userMounts[$oldMountPoint]);

    $this->userMountCache->removeMount($oldMountPoint);
    $this->userMountCache->addMount($recipient, $newMountPoint, new CacheEntry([
        'fileid' => $mount->getRootId(),
        'storage' => $mount->getStorageId(),
    ]), $mount->getMountProvider(), $mount->getMountId());
}

Patched it locally like this and the step completed over all 907 shares without further issues. Changing catch (\Exception ...) to catch (\Throwable ...) might also be worth considering so a single bad share can't abort the whole run.

Steps to reproduce

1. Have user/group shares whose file_target matches % (_) (_)% (duplicated conflict suffixes like Folder (2) (2))
2. Make sure at least one recipient of such a share has no row in oc_mounts for that target (e.g. a user who hasn't logged in since the share was created)
3. Run occ maintenance:repair --include-expensive

Expected behavior

The repair step should skip (or log) shares whose mount info is not cached, and finish the run.

Environment

• Nextcloud Server 34.0.3 (upgraded from 33.0.x)
• PostgreSQL, Apache, Linux

Full stack trace

Error: Call to a member function getRootId() on null in apps/files_sharing/lib/Repair/CleanupShareTarget.php:128
Stack trace:
#0 lib/private/Repair.php(104): OCA\Files_Sharing\Repair\CleanupShareTarget->run()
#1 core/Command/Maintenance/Repair.php(96): OC\Repair->run()
#2 3rdparty/symfony/console/Command/Command.php(326): OC\Core\Command\Maintenance\Repair->execute()
#3 3rdparty/symfony/console/Application.php(1098): Symfony\Component\Console\Command\Command->run()
#4 3rdparty/symfony/console/Application.php(324): Symfony\Component\Console\Application->doRunCommand()
#5 3rdparty/symfony/console/Application.php(175): Symfony\Component\Console\Application->doRun()
#6 lib/private/Console/Application.php(209): Symfony\Component\Console\Application->run()
#7 console.php(92): OC\Console\Application->run()
#8 occ(33): require_once('...')
#9 {main}