Fix render settings not saving when rendering (fixes #425)

Clicking Cancel or Add to Queue does save them but clicking Render does not.

This is caused by the fact that the GuiRenderSettings are now a popup and no
longer their own screen, so to close them, we need to call its close method, not
close the entire screen.

src/main/java/com/replaymod/render/gui/GuiRenderSettings.java

@@ -252,7 +252,7 @@ public class GuiRenderSettings extends AbstractGuiPopup<GuiRenderSettings> {
         @Override
         public void run() {
             // Closing this GUI ensures that settings are saved
-            getMinecraft().openScreen(null);
+            close();
             try {
                 VideoRenderer videoRenderer = new VideoRenderer(save(false), replayHandler, timeline);
                 videoRenderer.renderVideo();