account for the fact that we could be trying to decode nil, because w…

…e want to read past the next ResponseBody

rpc/bsonrpc/bsoncoders.go

@@ -44,8 +44,10 @@ func NewDecoder(r io.Reader) *Decoder {
 }
 
 func (d *Decoder) Decode(pv interface{}) (err error) {
-	rv := reflect.ValueOf(pv)
-	log.Println(log.TRACE, "Decoding into: ", rv.Type())
+	if pv != nil {
+		rv := reflect.ValueOf(pv)
+		log.Println(log.TRACE, "Decoding into: ", rv.Type())
+	}
 
 	var lbuf [4]byte
 	n, err := d.r.Read(lbuf[:])
@@ -80,7 +82,9 @@ func (d *Decoder) Decode(pv interface{}) (err error) {
 		log.Println(log.ERROR, "Error decoding message (reading message): ", err)
 	}
 
-	err = bson.Unmarshal(buf, pv)
+	if pv != nil {
+		err = bson.Unmarshal(buf, pv)
+	}
 
 	return
 }