From c4c188f6d9f85a92cb4a423a9d99402892b9a991 Mon Sep 17 00:00:00 2001
From: Andras Banki-Horvath <bhandras@gmail.com>
Date: Thu, 5 May 2022 20:20:03 +0200
Subject: [PATCH] signer: fix crash when musig combine doesn't have final sig

---
 lnrpc/signrpc/signer_server.go | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/lnrpc/signrpc/signer_server.go b/lnrpc/signrpc/signer_server.go
index ba98f276d..36a9de6fa 100644
--- a/lnrpc/signrpc/signer_server.go
+++ b/lnrpc/signrpc/signer_server.go
@@ -938,10 +938,15 @@ func (s *Server) MuSig2CombineSig(_ context.Context,
 		return nil, fmt.Errorf("error combining signatures: %v", err)
 	}
 
-	return &MuSig2CombineSigResponse{
+	resp := &MuSig2CombineSigResponse{
 		HaveAllSignatures: haveAllSigs,
-		FinalSignature:    finalSig.Serialize(),
-	}, nil
+	}
+
+	if haveAllSigs {
+		resp.FinalSignature = finalSig.Serialize()
+	}
+
+	return resp, err
 }
 
 // MuSig2Cleanup removes a session from memory to free up resources.