[BUG] Avatar is not loaded for username with special chars

[martin-v]

Fider Cloud or Self Hosted Self Hosted

Describe the bug For usernames like ´John Doe (Random Inc)orMaxi (he/him)` the avatar is not loaded.

To Reproduce Steps to reproduce the behavior:

1. Change username to something like above
2. Click on random page with avatar
3. See error

Expected behavior Avatar should work for all usernames.