Jay,
That is a good first stab. But you need to find out what is null. The following line...

Code:
SearchResponse response = service.Search(request);
What does service.Search return. Does it Always return a valid response or could it return null.

If it always returns something, will it always have an image.

So the thing that is returning null could be.
response OR
response.Image

I would like to think if you had an image you would always have a mediaURL.

Hope this helps.