Remote shares use local avatar

[nickvergessen]

Steps to reproduce

1. Create a local user "test1" and upload an avatar
2. As admin start a remote share with "test1@try.nextcloud.com"
3. Be confused because the avatar of "test1" from your dev instance is shown 😕

Expected behaviour

Placeholder avatar is shown

Actual behaviour

Local avatar is shown

I think this is a regression from the Vue sidebar? So cc @skjnldsv