From 3e111e7f58f9a3f38a73a9027f707b449fbf81ee Mon Sep 17 00:00:00 2001
From: Daniel Gultsch <daniel@gultsch.de>
Date: Sat, 27 Jan 2018 09:15:47 +0100
Subject: [PATCH] allow axolotl header to be empty in empty mucs

---
 .../siacs/conversations/crypto/axolotl/AxolotlService.java | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/main/java/eu/siacs/conversations/crypto/axolotl/AxolotlService.java b/src/main/java/eu/siacs/conversations/crypto/axolotl/AxolotlService.java
index a202a4c66..6f88e80d9 100644
--- a/src/main/java/eu/siacs/conversations/crypto/axolotl/AxolotlService.java
+++ b/src/main/java/eu/siacs/conversations/crypto/axolotl/AxolotlService.java
@@ -1212,10 +1212,11 @@ public class AxolotlService implements OnAdvancedStreamFeaturesLoaded {
 	}
 
 	@Nullable
-	private boolean buildHeader(XmppAxolotlMessage axolotlMessage, Conversation conversation) {
-		Set<XmppAxolotlSession> remoteSessions = findSessionsForConversation(conversation);
+	private boolean buildHeader(XmppAxolotlMessage axolotlMessage, Conversation c) {
+		Set<XmppAxolotlSession> remoteSessions = findSessionsForConversation(c);
+		final boolean acceptEmpty = c.getMode() == Conversation.MODE_MULTI && c.getMucOptions().getUserCount() == 0;
 		Collection<XmppAxolotlSession> ownSessions = findOwnSessions();
-		if (remoteSessions.isEmpty()) {
+		if (remoteSessions.isEmpty() && !acceptEmpty) {
 			return false;
 		}
 		for (XmppAxolotlSession session : remoteSessions) {