[BUG] When the backend lost connection to a mount, accessing ressoures behave strange

If you found a bug:

When the backend (temporarily) loses connection to a mount, IOS does not show any note / error message when accessing the inaccessible mount. Happened while my SMB backend was temporarily inaccessible.

Steps to reproduce

1. have a mount with r/w permissions
2. make the backend inaccessible
3. try to access a file (open or open with) - file not present
4. force reloading the folder where the mount is inaccessible = all in sync ??
5. try to access a file - file not present
6. change folder - ok ??? (why, mount is inaccessible)

Expected behavior

Proper error message that the mount is temporarily inaccessible

Actual behavior

Folder change ok (??)
File access - not found

Idea

Check if mount is temporarily unavailable and show this if:

• When a file returns "not found"
• When forcing a reload (swipe down screen)

Client

iOS version: 14.6

ownCloud app version: 11.6.0

Device model: iPad/iPhone

Server configuration

Web server: nginx

Database: mariadb

PHP version: 7.4

ownCloud version: 10.7

Storage backend (external storage): local, smb, gd

Logs

Web server error log

Nothing relevant

ownCloud log (data/owncloud.log)

Nothing relevant

@michaelstingl @hosy fyi

Start by reproducing the issue on iOS with an inaccessible SMB mount, following the listed file-access and forced-reload steps. Trace how the app handles missing files and folder reloads, then verify that a temporarily unavailable mount produces a proper error instead of a not-found result or apparently successful navigation.