Fix a panic when management is behind an invalid proxy (#1930)

- Add a new error on gRPC client that doesn't pass the incorrect status from the gRPC client
- Try login only if we have a server public key

client/internal/login.go

@@ -68,7 +68,7 @@ func Login(ctx context.Context, config *Config, setupKey string, jwtToken string
 	}
 
 	serverKey, err := doMgmLogin(ctx, mgmClient, pubSSHKey)
-	if isRegistrationNeeded(err) {
+	if serverKey != nil && isRegistrationNeeded(err) {
 		log.Debugf("peer registration required")
 		_, err = registerPeer(ctx, *serverKey, mgmClient, setupKey, jwtToken, pubSSHKey)
 		return err