Prefill doesn't seem to have an effect

How do I get prefill to work? Take the following slightly modified example:

**Test case:** https://codepen.io/armin-m-ller/pen/OYQjyj

Resize the browser window to < 780px, this will result in all initially loaded images to fit completely, i.e. there will be no scroll bar and subsequently, no way for the user to trigger loading the next page(s).

**Expected behavior:** prefill option to actually load the 2nd page in case all images fit on the first load..

Start with the linked CodePen and reproduce the behavior below 780px, then trace the infinite-scroll prefill option from the plugin entry point. Done means that when the first page's images fit without a scrollbar, prefill loads the second page automatically.

Written by the indexing model from the issue text.