"PHP Warning: Attempt to read property on null" in themes/learn.jquery.com/sidebar.php

[Krinkle]

krinkle@wp-04:/var/log/nginx$ tail -f error.log 

PHP Warning:  Attempt to read property "post_parent" on null
in /srv/wordpress/jquery-wp-content/themes/learn.jquery.com/sidebar.php on line 35
PHP Warning:  Attempt to read property "ID" on null
in /srv/wordpress/jquery-wp-content/themes/learn.jquery.com/sidebar.php on line 15

PHP Warning:  Attempt to read property "post_parent" on null
in /srv/wordpress/jquery-wp-content/themes/learn.jquery.com/sidebar.php on line 35
PHP Warning:  Attempt to read property "ID" on null
in /srv/wordpress/jquery-wp-content/themes/learn.jquery.com/sidebar.php on line 35

krinkle@wp-04:/var/log/nginx$ ls -halF
1.1G error.log

This is reproducible via URLs such as https://learn.jquery.com/?s=findnothingnothingatall