message: Set a clear color when no IBL is present
diff: #include <filament/LightManager.h>
  #include <filament/Material.h>
  #include <filament/MaterialInstance.h>
  +#include <filament/Renderer.h>
  #include <filament/RenderableManager.h>
  #include <filament/Scene.h>
  #include <filament/TransformManager.h>
  @@ -665,7 +666,7 @@ static void gui(filament::Engine* engine, filament::View*) {
  params.spotLightConeAngle);
  }
  -static void preRender(filament::Engine*, filament::View* view, filament::Scene*, filament::Renderer*) {
  +static void preRender(filament::Engine*, filament::View* view, filament::Scene*, filament::Renderer* renderer) {
  view->setAntiAliasing(g_params.fxaa ? View::AntiAliasing::FXAA : View::AntiAliasing::NONE);
  view->setToneMapping(g_params.tonemapping ? View::ToneMapping::ACES : View::ToneMapping::LINEAR);
  view->setDithering(g_params.dithering ? View::Dithering::TEMPORAL : View::Dithering::NONE);
  @@ -676,6 +677,11 @@ static void preRender(filament::Engine*, filament::View* view, filament::Scene*,
  g_params.ssao ? View::AmbientOcclusion::SSAO : View::AmbientOcclusion::NONE);
  view->setAmbientOcclusionOptions(g_params.ssaoOptions);
  + // Without an IBL, we must clear the swapchain to black before each frame.
  + renderer->setClearOptions({
  + .clearColor = { 0.0f, 0.0f, 0.0f, 1.0f },
  + .clear = !FilamentApp::get().getIBL() });
  +
  Camera& camera = view->getCamera();
  camera.setExposure(g_params.cameraAperture, 1.0f / g_params.cameraSpeed, g_params.cameraISO);
  }
  