Gui: modernize C++: use equals default

src/Gui/DlgEditFileIncludePropertyExternal.cpp

@@ -49,11 +49,7 @@ DlgEditFileIncludePropertyExternal(App::PropertyFileIncluded& Prop,
 /**
  *  Destroys the object and frees any allocated resources
  */
-DlgEditFileIncludePropertyExternal::~DlgEditFileIncludePropertyExternal()
-{
-    // no need to delete child widgets, Qt does it all for us
-}
-
+DlgEditFileIncludePropertyExternal::~DlgEditFileIncludePropertyExternal() = default;
 
 int DlgEditFileIncludePropertyExternal::processFile()
 {