do not loop requesting vcard when opening a chat window with ourself and we don't have a vcard stored on server

do not crash when we remove a contact for which neerby contcts are not in the same accounts. Fixes #8157

request archiving preferences only if server announce it supports it, and don't think it supports it while it's buggy. Fixes #7839

show error message when we try to connect anonymously to a server that doesn't support anonymous connection. Fixes #8138