Fixed different behaviour between transaction parsing from wire or JSON

JSON version sometimes returned nil Address field in ScriptPubKey (if
it was omitted in input JSON) but wire version always returned allocated
empty slice.

bchain/coins/btc/bitcoinparser.go

@@ -113,9 +113,11 @@ func (p *BitcoinParser) TxFromMsgTx(t *wire.MsgTx, parseAddresses bool) bchain.T
 	}
 	vout := make([]bchain.Vout, len(t.TxOut))
 	for i, out := range t.TxOut {
-		addrs := []string{}
+		var addrs []string
 		if parseAddresses {
-			addrs, _ = p.OutputScriptToAddresses(out.PkScript)
+			if tmp, _ := p.OutputScriptToAddresses(out.PkScript); len(tmp) > 0 {
+				addrs = tmp
+			}
 		}
 		s := bchain.ScriptPubKey{
 			Hex:       hex.EncodeToString(out.PkScript),