[PHP 7.3] compact warning upgrade

[TomasVotruba]

https://www.php.net/manual/en/function.compact.php

Note:

Before PHP 7.3, any strings that are not set will silently be skipped.

Upgrade path

• https://3v4l.org/bZ61T
• remove all non-set variables

 $value = 'yes';

-compact('value', 'non_existing');
+compact('value');