fix up no-op-renderer

test/no_op_renderer.hpp

diff --git a/test/no_op_renderer.hpp b/test/no_op_renderer.hpp
index cf23493..6610dec 100644
--- a/test/no_op_renderer.hpp
+++ b/test/no_op_renderer.hpp
@@ -9,6 +9,9 @@
         bool decode(const uint8_t* bytes, std::size_t size) override {
             return true;
         }
+        rcp<RenderShader> makeShader(RenderTileMode, RenderTileMode, const Mat2D*) const override {
+            return nullptr;
+        }
     };
 
     class NoOpRenderPaint : public RenderPaint {