Preview of Null file is requested when "Transfer" tab is open

When uploading my photo library I discovered that there are many 404s in my access log. These request a preview of an empty file id. This only occurs when I have the "Transfer" tab is open.

Steps to reproduce

1. Upload files via Automatic Photo Uploading
2. Open "Transfer" tab

The following requests appear en-masse in my access log (dozens per second after uploading a file) wh

2024-12-22 10:43:36	Error	2003:e5:9f13:c800:502e:xxxx	404	GET /index.php/core/preview?fileId=&x=1024&y=1024&a=1&mode=cover&forceIcon=0&mimeFallback=0 HTTP/1.0

the iOS log says the following about this:

2024-12-22 10:51:22 [INFO] Upload complete https://nextcloudinstance.dummy.de/remote.php/dav/files/Simon/Camera Uploads/2016-08-14 18-11-45_2235.mov, result: success(19183362 bytes)
2024-12-22 10:51:23 Network request started: GET https://nextcloudinstance.dummy.de/index.php/core/preview?fileId=&x=1024&y=1024&a=1&mode=cover&forceIcon=0&mimeFallback=0
2024-12-22 10:51:23 Network request headers: ["Content-Type": "application/x-www-form-urlencoded", "OCS-APIRequest": "true", "User-Agent": "Mozilla/5.0 (iOS) Nextcloud-iOS/6.2.1", "Accept": "application/json", "Authorization": "Basic TOKENRETRACTED"]
2024-12-22 10:51:23 Network request body: None
2024-12-22 10:51:23 Network request started: GET https://nextcloudinstance.dummy.de/index.php/core/preview?fileId=&x=1024&y=1024&a=1&mode=cover&forceIcon=0&mimeFallback=0
2024-12-22 10:51:23 Network request headers: ["Content-Type": "application/x-www-form-urlencoded", "OCS-APIRequest": "true", "User-Agent": "Mozilla/5.0 (iOS) Nextcloud-iOS/6.2.1", "Accept": "application/json", "Authorization": "Basic TOKENRETRACTED"]
2024-12-22 10:51:23 Network request body: None
2024-12-22 10:51:23 Network request started: GET https://nextcloudinstance.dummy.de/index.php/core/preview?fileId=&x=1024&y=1024&a=1&mode=cover&forceIcon=0&mimeFallback=0
2024-12-22 10:51:23 Network request headers: ["Content-Type": "application/x-www-form-urlencoded", "OCS-APIRequest": "true", "User-Agent": "Mozilla/5.0 (iOS) Nextcloud-iOS/6.2.1", "Accept": "application/json", "Authorization": "Basic TOKENRETRACTED"]
2024-12-22 10:51:23 Network request body: None
2024-12-22 10:51:23 Network request started: GET https://nextcloudinstance.dummy.de/index.php/core/preview?fileId=&x=1024&y=1024&a=1&mode=cover&forceIcon=0&mimeFallback=0
2024-12-22 10:51:23 Network request headers: ["Content-Type": "application/x-www-form-urlencoded", "OCS-APIRequest": "true", "User-Agent": "Mozilla/5.0 (iOS) Nextcloud-iOS/6.2.1", "Authorization": "Basic TOKENRETRACTED", "Accept": "application/json"]
2024-12-22 10:51:23 Network request body: None

Environment data

iOS version: 18

Nextcloud iOS app version: 6.2.1.0

Server operating system:

Web server: Apache, nginx

PHP version: 8.3

Nextcloud version: 30.0.4

Start by reproducing the issue with Automatic Photo Uploading while the Transfer tab is open, and inspect the preview requests shown in the report. Trace why requests are sent with an empty fileId; done means uploads no longer trigger repeated preview requests for an empty file.