CHUI-824 FIXED Open Message panel when session is activated.

indra/newview/llfloaterimcontainer.cpp

@@ -114,6 +114,7 @@ void LLFloaterIMContainer::sessionAdded(const LLUUID& session_id, const std::str
 void LLFloaterIMContainer::sessionActivated(const LLUUID& session_id, const std::string& name, const LLUUID& other_participant_id)
 {
 	selectConversationPair(session_id, true);
+	collapseMessagesPane(false);
 }
 
 void LLFloaterIMContainer::sessionVoiceOrIMStarted(const LLUUID& session_id)