Gui: modernize C++: use equals default

src/Gui/PropertyPage.cpp

@@ -144,9 +144,7 @@ PreferenceUiForm::PreferenceUiForm(const QString& fn, QWidget* parent)
     }
 }
 
-PreferenceUiForm::~PreferenceUiForm()
-{
-}
+PreferenceUiForm::~PreferenceUiForm() = default;
 
 void PreferenceUiForm::changeEvent(QEvent *e)
 {
@@ -219,9 +217,7 @@ CustomizeActionPage::CustomizeActionPage(QWidget* parent) : QWidget(parent)
 }
 
 /** Destruction */
-CustomizeActionPage::~CustomizeActionPage()
-{
-}
+CustomizeActionPage::~CustomizeActionPage() = default;
 
 bool CustomizeActionPage::event(QEvent* e)
 {