ValueError in createFileKey() when results array is empty and S3 file exists

Problem/Motivation

When uploading a file whose name already exists on S3 but the s3fs cache table has no matching records (stale cache), AjaxController::createFileKey() crashes on line 172 with:

ValueError: max(): Argument #1 ($value) must contain at least one element in max()

The call max(array_keys($results)) fails because $results is empty when the LIKE query on s3fs_file returns no matching URIs, but the file already exists on S3 (detected by doesObjectExistV2).

Steps to reproduce

1. Upload a file via an s3fs_cors widget (e.g. a video file)
2. Upload a file with the same name again
3. If the s3fs cache table is stale (does not contain the first file's record), the rename logic enters the cache-stale branch on line 167 but crashes because $results is empty

Proposed resolution

Guard the max() call on line 172 so it defaults to 0 when $results is empty:

$suffix = $results !== [] ? max(array_keys($results)) : 0;

Remaining tasks

Review and commit the merge request.

User interface changes

None.

API changes

None.

Data model changes

None.