Version 4.9.4: Workaround MSVC optimization bug.

When adding some de-optimizing code, like logging etc,
the issue disappears. This volatile workaround looks like it works.

Telegram/SourceFiles/dialogs/dialogs_main_list.cpp

@@ -194,6 +194,11 @@ UnreadState MainList::unreadState() const {
 		result.chatsMuted = result.chats;
 		result.marksMuted = result.marks;
 	}
+	volatile auto touch = _unreadState.marks + _unreadState.marksMuted
+		+ _unreadState.messages + _unreadState.messagesMuted
+		+ _unreadState.chats + _unreadState.chatsMuted
+		+ _unreadState.reactions + _unreadState.reactionsMuted
+		+ _unreadState.mentions;
 	return result;
 }