windowscodecs: IWICMetadataQueryReader::GetMetadataByName() should accept NULL for returned value.

dlls/windowscodecs/metadataquery.c

@@ -589,7 +589,7 @@ static HRESULT WINAPI mqr_GetMetadataByName(IWICMetadataQueryReader *iface, LPCW
     PropVariantClear(&tk_id);
     PropVariantClear(&tk_schema);
 
-    if (hr == S_OK)
+    if (hr == S_OK && value)
         *value = new_value;
     else
         PropVariantClear(&new_value);

dlls/windowscodecs/tests/metadata.c

@@ -1606,6 +1606,10 @@ static void test_metadata_gif(void)
             if (winetest_debug > 1)
                 trace("query: %s\n", decoder_data[i].query);
             MultiByteToWideChar(CP_ACP, 0, decoder_data[i].query, -1, queryW, 256);
+
+            hr = IWICMetadataQueryReader_GetMetadataByName(queryreader, queryW, NULL);
+            ok(hr == decoder_data[i].hr, "GetMetadataByName(%s) returned %#x, expected %#x\n", wine_dbgstr_w(queryW), hr, decoder_data[i].hr);
+
             PropVariantInit(&value);
             hr = IWICMetadataQueryReader_GetMetadataByName(queryreader, queryW, &value);
             ok(hr == decoder_data[i].hr, "GetMetadataByName(%s) returned %#x, expected %#x\n", wine_dbgstr_w(queryW), hr, decoder_data[i].hr);