Add support for programmable samplers in shaders

Source/Engine/GraphicsDevice/Null/GPUSamplerNull.h

@@ -0,0 +1,23 @@
+// Copyright (c) 2012-2021 Wojciech Figat. All rights reserved.
+
+#pragma once
+
+#if GRAPHICS_API_NULL
+
+#include "Engine/Graphics/Textures/GPUSampler.h"
+
+/// <summary>
+/// Sampler object for Null backend.
+/// </summary>
+class GPUSamplerNull : public GPUSampler
+{
+protected:
+
+    // [GPUSampler]
+    bool OnInit() override
+    {
+        return false;
+    }
+};
+
+#endif