Fetching the first entry in a grid

I am trying to populate the og:image meta tag. My template uses a fluid field (westeros_data) which has includes the ability to add single images or file grids of images. A post may have neither, either or both. If there’s neither, og:image gets no data (I am considering assigning a default image, however). If there’s either, og:image should get either the first single image or the first image from the grid. If there is both, og:image shoiuld get the first single image.

I have it working so it fetches the first single image:

{westeros_data}{westeros_data:westeros_image}{if {westeros_data:count name="westeros_image"} == "1"}{content}{content:image}{/content}{/if}{/westeros_data:westeros_image}

But I am not sure how to grab a single image from a file grid or to create a conditional in the case where a post has both a single image and a file grid with images.