wallet: return ErrNotMine for script addresses

We recently added the ManagedTaprootScriptAddress type which is not a
ManagedPubKeyAddress and therefore doesn't store the derivation info.
When trying to fetch the input info for such an address we run into the
case where we return nil as the error which causes issues further up in
the call stack.
This commit fixes the problem by returning an actual error and not the
err variable that is nil due to the previous check.

wallet/utxos.go

@@ -135,7 +135,7 @@ func (w *Wallet) FetchInputInfo(prevOut *wire.OutPoint) (*wire.MsgTx,
 	}
 	pubKeyAddr, ok := addr.(waddrmgr.ManagedPubKeyAddress)
 	if !ok {
-		return nil, nil, nil, 0, err
+		return nil, nil, nil, 0, ErrNotMine
 	}
 	keyScope, derivationPath, _ := pubKeyAddr.DerivationInfo()