agent: Skip unknown unknown ssh curves seen on cards.
* agent/command-ssh.c (ssh_handler_request_identities): Skip unknown curves.
For example when using my standard ed25519 token and testing cards
with only Brainpool support, the ssh-agent failed due to the unknown
curves seen on the card. This patches fixes this by ignoring keys
with unknown curves.
- Signed-off-by: Werner Koch <email@example.com>