Cannot read property 'top' of undefined in belowEntryMetaClass (TwentySeventeen)

[ericdaams]

I'm seeing this with TwentySeventeen version 1.3 activated:

global.js?ver=1.0:124 Uncaught TypeError: Cannot read property 'top' of undefined
    at belowEntryMetaClass (global.js?ver=1.0:124)
    at global.js?ver=1.0:239

It only occurs in the following circumstance:

• You have widgets in the sidebar menu.
• You have a custom template (either defined in your child theme or generated by a plugin) that does not load the sidebar.

If the above are both true, you'll see the error triggered on the window.resize event.

I first encountered this while testing alongside ​Charitable (create a campaign and then go to donate page), but you can also reproduce by creating a child theme and adding a custom single.php with the sidebar omitted.

[ericdaams]

I've added two patches, either of which resolves this. The second is a little more efficient since it only checks $sidebar.length instead of also checking for the has-sidebar body class. My assumption is that if $sidebar.length is false, has-sidebar will never exist as a body class anyway, so it's a redundant check.