rm unused parameter

GUI/Model/Session/SessionModel.cpp

@@ -382,11 +382,9 @@ void SessionModel::readFrom(QXmlStreamReader* reader, MessageService* messageSer
     endResetModel();
 }
 
-void SessionModel::writeTo(QXmlStreamWriter* writer, SessionItem* parent)
+void SessionModel::writeTo(QXmlStreamWriter* writer)
 {
-    if (!parent)
-        parent = m_root_item;
-    GUI::Session::XML::writeTo(writer, parent);
+    GUI::Session::XML::writeTo(writer, m_root_item);
 }
 
 //! Move given parameterized item to the new_parent at given row. If new_parent is not defined,

GUI/Model/Session/SessionModel.h

@@ -99,7 +99,7 @@ public:
     SessionItem* itemForIndex(const QModelIndex& index) const;
 
     virtual void readFrom(QXmlStreamReader* reader, MessageService* messageService = nullptr);
-    virtual void writeTo(QXmlStreamWriter* writer, SessionItem* parent = nullptr);
+    virtual void writeTo(QXmlStreamWriter* writer);
 
     SessionItem* moveItem(SessionItem* item, SessionItem* new_parent = nullptr, int row = -1,
                           const QString& tag = "");