MP Create Game: replaced a hack with a proper solution

src/gui/dialogs/multiplayer/mp_create_game.cpp

@@ -307,6 +307,11 @@ void mp_create_game::pre_show(window& win)
 	connect_signal_notify_modified(tab_bar,
 		std::bind(&mp_create_game::on_tab_select, this, std::ref(win)));
 
+	// Allow the settings stack to find widgets in all pages, regardless of which is selected.
+	// This ensures settings (especially game settings) widgets are appropriately updated when
+	// a new game is selected, regardless of which settings tab is active at the time.
+	find_widget<stacked_widget>(&win, "pager", false).set_find_in_all_layers(true);
+
 	// We call on_tab_select farther down.
 
 	//
@@ -520,22 +525,6 @@ void mp_create_game::on_tab_select(window& window)
 {
 	const int i = find_widget<listbox>(&window, "tab_bar", false).get_selected_row();
 	find_widget<stacked_widget>(&window, "pager", false).select_layer(i);
-
-	/* HACK: the GUI2 field functions always internally save the correct value when set_widget_value is called
-	 *       - ie, when on_game_select calls update_map_settings, the correct values will be stored in the field,
-	 *       but if the settings tab isn't selected the widgets will not display the correct values. This forces
-	 *       an update when we switch to that tab so the widgets correctly display their values.
-	 *
-	 *       A possible better fix would be storing a pointer to the widget in question in the field object. It
-	 *       seems widgets will still correctly update even if they are not on the currently selected page if a
-	 *       pointer already exists.
-	 *
-	 *       Another possible fix would be allowing stacked_widget to return widgets on any page, not just on the
-	 *       currently visible one.
-	 */
-	if(i == TAB_SETTINGS) {
-		update_map_settings(window);
-	}
 }
 
 void mp_create_game::on_mod_toggle(window& window, const int index, toggle_button* sender)