fix: Skip registering mount points for missing owner node

[juliushaertl]

Make sure that we don't show share mount points where the owner node is not available anymore.

steps to reproduce:

• share a file with user1 (share_with) as user2 (uid_initiator) owned by user3 (uid_owner)
• create group1
• add user2 and user3 as members to group1
• create groupfolder for group1
• as user3, move the file into the new groupfolder
• the share still has user1 as share_with, user2 as uid_initiator and user3 as uid_owner and is accessible
• remove user3 from group1

🛑 the shared file is still shown but user1 cannot access the file anymore

This still leaves an orphaned share entry but so far I had no luck finding a proper sql query so that we could add this to

server/apps/files_sharing/lib/DeleteOrphanedSharesJob.php

Line 33 in a0f6a65

class DeleteOrphanedSharesJob extends TimedJob {

however skipping the share mount will at least avoid broken files being shown to users.

[come-nc]

The root problem is in the move logic no, it should somehow update the share info?

[icewind1991]

This is a pretty expensive operation to perform for each incoming share and will kill performance for users with a large number of incoming shares.

[icewind1991]

It's probably better to catch this error when the user tries to interact with the broken. That way it doesn't have to run this check for N shares

[juliushaertl]

I lack time to finish this, so I'll close for now. We can reopen anyways if we need.