don't crash when refraction pass is empty

filament/src/RenderPass.h

@@ -280,6 +280,7 @@ public:
 
     Command const* begin() const noexcept { return mCommandBegin; }
     Command const* end() const noexcept { return mCommandEnd; }
+    bool empty() const noexcept { return begin() == end(); }
 
     // This is the main function of this class, this appends commands to the pass using
     // the current camera, geometry and flags set. This can be called multiple times if needed.

filament/src/Renderer.cpp

@@ -497,7 +497,7 @@ void FRenderer::renderJob(ArenaScope& arena, FView& view) {
 
     // the color pass + refraction + color-grading as subpass if needed
     // this cancels the colorPass() call above if refraction is active.
-    if (view.isScreenSpaceRefractionEnabled()) {
+    if (view.isScreenSpaceRefractionEnabled() && !pass.empty()) {
         colorPassOutput = refractionPass(fg, config, colorGradingConfigForColor, pass, view);
     }