tapfreighter: don't use proof courier for pre-signed parcel

Since a pre-signed parcel (a parcel that uses the RPC driven vPSBT flow)
doesn't have proof courier URLs (they aren't part of the vPSBT), the
proofs must always be delivered in an interactive manner from sender to
receiver and we don't even need to attempt to use a proof courier.

Author: guggero

tapfreighter/chain_porter.go

@@ -699,8 +699,14 @@ func (p *ChainPorter) transferReceiverProof(pkg *sendPackage) error {
 	}
 
 	// If we have a proof courier instance active, then we'll launch several
-	// goroutines to deliver the proof(s) to the receiver(s).
-	if p.cfg.ProofCourierCfg != nil {
+	// goroutines to deliver the proof(s) to the receiver(s). Since a
+	// pre-signed parcel (a parcel that uses the RPC driven vPSBT flow)
+	// doesn't have proof courier URLs (they aren't part of the vPSBT), the
+	// proofs must always be delivered in an interactive manner from sender
+	// to receiver, and we don't even need to attempt to use a proof
+	// courier.
+	_, isPreSigned := pkg.Parcel.(*PreSignedParcel)
+	if p.cfg.ProofCourierCfg != nil && !isPreSigned {
 		ctx, cancel := p.WithCtxQuitNoTimeout()
 		defer cancel()