fix #LINQT-1774 forgot to set visible property en e2e encrypted header

Linphone/core/chat/ChatCore.cpp

@@ -261,6 +261,10 @@ bool ChatCore::isGroupChat() const {
 	return mIsGroupChat;
 }
 
+bool ChatCore::isEncrypted() const {
+	return mIsEncrypted;
+}
+
 QString ChatCore::getIdentifier() const {
 	return mIdentifier;
 }

Linphone/core/chat/ChatCore.hpp

@@ -66,6 +66,8 @@ public:
 
 	bool isGroupChat() const;
 
+	bool isEncrypted() const;
+
 	QString getIdentifier() const;
 
 	ChatMessageGui *getLastMessage() const;

Linphone/view/Control/Display/Chat/ChatMessagesListView.qml

@@ -59,6 +59,7 @@ ListView {
     }
 
     header: Item {
+        visible: mainItem.chat && mainItem.chat.core.isEncrypted
         height: headerMessage.height + Math.round(50 * DefaultStyle.dp)
         width: headerMessage.width
         anchors.horizontalCenter: parent.horizontalCenter