PHP Notice in fb_instant_articles_rss_form_node_form_alter when creating new content

With the fb_instant_articles_rss module enabled, when you create new content you get the following PHP notice:

Notice: Undefined property: stdClass::$nid in fb_instant_articles_rss_form_node_form_alter() (line 181 of /var/www/docroot/sites/all/modules/contrib/fb_instant_articles/modules/fb_instant_articles_rss/fb_instant_articles_rss.module).

This is due to assuming a nid when there isn't one yet.