[UWP] Memory leak in IsBackgroundImageValid

[paulcam206]

AdaptiveCards/source/uwp/Renderer/lib/Util.cpp

Lines 1313 to 1328 in 10dd6f3

	HRESULT IsBackgroundImageValid(_In_ ABI::AdaptiveNamespace::IAdaptiveBackgroundImage* backgroundImageElement, _Out_ BOOL* isValid)
	{
	ComPtr<ABI::AdaptiveNamespace::IAdaptiveBackgroundImage> backgroundImage(backgroundImageElement);
	if (backgroundImage != NULL)
	{
	HSTRING url;
	THROW_IF_FAILED(backgroundImage->get_Url(&url));
	if (url != NULL)
	{
	*isValid = TRUE;
	return S_OK;
	}
	}
	*isValid = FALSE;
	return S_OK;
	}

url gets leaked because it's an HSTRING, not an HString