Forcing a print bed update after config or config bundle is loaded.

The solution is hackish, but a major refactoring would be needed
to avoid multiple refreshes of the print bed, and to avoid
expensive checks at Plater::on_config_change() every time
a config value changes at a parameter tab.

src/slic3r/GUI/GUI_App.cpp

@@ -960,8 +960,11 @@ void GUI_App::load_current_presets()
 	this->plater()->set_printer_technology(printer_technology);
     for (Tab *tab : tabs_list)
 		if (tab->supports_printer_technology(printer_technology)) {
-			if (tab->type() == Preset::TYPE_PRINTER)
+			if (tab->type() == Preset::TYPE_PRINTER) {
 				static_cast<TabPrinter*>(tab)->update_pages();
+				// Mark the plater to update print bed by tab->load_current_preset() from Plater::on_config_change().
+				this->plater()->force_print_bed_update();
+			}
 			tab->load_current_preset();
 		}
 }