How do I check for the presence of an asset before accessing an empty asset field?
You could just check the length of the whole asset array first, to make sure there are two images. Something like this:

{% if (entry.igBanner | length) &gt; 1 %}
    {% set asset = entry.igBanner[1] %}
    &lt;img src={{ asset.url }} class="img-responsive" alt={{entry.title}}&gt;
{% endif %}