reimplemented updating UI from effect fields

effects/fields/stringfield.h

@@ -12,6 +12,7 @@ public:
   QString GetStringAt(double timecode);
 
   virtual QWidget *CreateWidget() override;
+  virtual void UpdateWidgetValue(QWidget* widget, double timecode) override;
 private slots:
   void UpdateFromWidget(const QString& b);
 };