d3dcompiler: Allow D3DCompile2() to succeed with null output shader blob pointer.

dlls/d3dcompiler_43/compiler.c

@@ -556,7 +556,7 @@ HRESULT WINAPI D3DCompile2(const void *data, SIZE_T data_size, const char *filen
             vkd3d_shader_free_messages(messages);
     }
 
-    if (!ret)
+    if (!ret && shader_blob)
     {
         if (FAILED(hr = D3DCreateBlob(byte_code.size, shader_blob)))
         {

dlls/d3dcompiler_43/tests/hlsl_d3d9.c

@@ -1742,6 +1742,22 @@ static void test_include(void)
     delete_directory(L"include");
 }
 
+static void test_no_output_blob(void)
+{
+    static const char vs_source[] =
+        "float4 main(float4 pos : POSITION, inout float2 texcoord : TEXCOORD0) : POSITION\n"
+        "{\n"
+        "   return pos;\n"
+        "}";
+    ID3D10Blob *errors;
+    HRESULT hr;
+
+    errors = (void *)0xdeadbeef;
+    hr = D3DCompile(vs_source, strlen(vs_source), NULL, NULL, NULL, "main", "vs_2_0", 0, 0, NULL, &errors);
+    ok(hr == S_OK, "Unexpected hr %#lx.\n", hr);
+    ok(!errors, "Unexpected errors blob.\n");
+}
+
 START_TEST(hlsl_d3d9)
 {
     HMODULE mod;
@@ -1770,4 +1786,5 @@ START_TEST(hlsl_d3d9)
     test_constant_table();
     test_fail();
     test_include();
+    test_no_output_blob();
 }