"add split" button now does something (thanks hemirt)

widgets/chatwidgetheader.cpp

@@ -157,7 +157,8 @@ void ChatWidgetHeader::rightButtonClicked()
 
 void ChatWidgetHeader::menuAddSplit()
 {
-    printf("Add split for menu (NOT IMPLEMENTED KKarrot)\n");
+    auto page = static_cast<NotebookPage *>(_chatWidget->parentWidget());
+    page->addChat();
 }
 void ChatWidgetHeader::menuCloseSplit()
 {

widgets/chatwidgetheader.h

@@ -24,7 +24,7 @@ class ChatWidgetHeader : public QWidget
 public:
     explicit ChatWidgetHeader(ChatWidget *parent);
 
-    ChatWidget *getChatWidget()
+    ChatWidget *getChatWidget() const
     {
         return _chatWidget;
     }
@@ -39,7 +39,7 @@ protected:
     void mouseDoubleClickEvent(QMouseEvent *event);
 
 private:
-    ChatWidget *_chatWidget;
+    ChatWidget * const _chatWidget;
 
     QPoint _dragStart;
     bool _dragging;