Loading of avatars fails with 500 error

[hurradieweltgehtunter]

Steps to reproduce

1. Load any file list where column "owner" or "shared with" is present (e.g. "Shared with me " or "shared with others")
2. AJAX Calls to load avatars fail (see dev console)

Expected behaviour

500 error should not happen

Actual behaviour

GET https://cloudurl.com//remote.php/dav/avatars/username/128.png fails with 500 status

Browser log

Error loading avatar image for user "archive":  Unexpected status code 500 core.bundle.js:366:52759
    setUser https://cloudurl.com/index.php/apps/web/core/core.bundle.js:366

[hurradieweltgehtunter]

Just saw that the avatar URL has a double slash:
cloudurl.com // remote.php/dav/avatars/username/128.png

Removing one slash manually and resending the request makes it return with a 404 (which might be because the user I tested with has no avatar). Anyhow, 404 is much better than 500.

[individual-it]

500 should not be returned anyway, if the client sends a wrong request the server should not return 500

ToDo QA-team:

• reproduce in what case 500 error are returned
• create (API) tests for that cases

[individual-it]

for me https://localhost:9200//remote.php/dav/avatars/admin/128.png is requested and 404 is returned
I've updated the topBar image in the tests here: #4773