packet.writeTo now defends against a zero pkt.bodySize.

rtmp/packet.go

@@ -272,7 +272,7 @@ func (pkt *packet) resize(size uint32, ht uint8) {
 // We defer sending small audio packets and combine consecutive small audio packets where possible to reduce I/O.
 // When queue is true, we expect a response to this request and cache the method on s.methodCalls.
 func (pkt *packet) writeTo(s *Session, queue bool) error {
-	if pkt.body == nil {
+	if pkt.body == nil || pkt.bodySize == 0 {
 		return errInvalidBody
 	}