lnwallet: fix InternalKeyForAddr for imported addr

An address imported using ImportTapscript doesn't provide a private key
so it can't satisfy waddrmgr.ManagedPubKeyAddress interface. So we don't
return an error for imported addresses.
Fix lightninglabs/loop#923

Author: starius

lnwallet/interface.go

@@ -662,6 +662,14 @@ func InternalKeyForAddr(wallet WalletController, netParams *chaincfg.Params,
 
 	pubKeyAddr, ok := walletAddr.(waddrmgr.ManagedPubKeyAddress)
 	if !ok {
+		// Imported addresses do not provide private keys, so they
+		// do not implement waddrmgr.ManagedPubKeyAddress.
+		// See RPC ImportTapscript.
+		// Fix https://github.com/lightninglabs/loop/issues/923
+		if walletAddr.Imported() {
+			return none, nil
+		}
+
 		return none, fmt.Errorf("expected pubkey addr, got %T",
 			walletAddr)
 	}