From f751566f000dc39eb478804ccfff33461b8ecd08 Mon Sep 17 00:00:00 2001
From: Marten Seemann <martenseemann@gmail.com>
Date: Thu, 19 May 2016 10:55:34 +0700
Subject: [PATCH] don't panic on failed type assertion in PacketPacker

related to #93
---
 packet_packer.go | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/packet_packer.go b/packet_packer.go
index c3e1065f..8750360e 100644
--- a/packet_packer.go
+++ b/packet_packer.go
@@ -195,7 +195,11 @@ func (p *packetPacker) composeNextPacket(stopWaitingFrame *frames.StopWaitingFra
 
 	// remove the dataLen for the last StreamFrame in the packet
 	if hasStreamFrames {
-		payloadFrames[len(payloadFrames)-1].(*frames.StreamFrame).DataLenPresent = false
+		lastStreamFrame, ok := payloadFrames[len(payloadFrames)-1].(*frames.StreamFrame)
+		if !ok {
+			return nil, errors.New("PacketPacker BUG: StreamFrame type assertion failed")
+		}
+		lastStreamFrame.DataLenPresent = false
 		// payloadLength -= 2
 	}