Multiple inappropriate array member references

Since moving a site using this plugin to PHP 7.2, I’ve noticed this in my Web server logs: PHP Warning: Use of undefined constant username - assumed 'username' (this will throw an Error in a future version of PHP) in /var/www/html/mysite.name.here/wp-content/plugins/wp-twitter-feed/class-frontend.php on line 52 There are a couple dozen instances of this, because a lot of the calls to members of $wptf in class-frontend.php aren’t quoted like they should be. On a lark, I tried single-quoting all those references, but then the plugin doesn’t seem to work. So, heads-up, while this plugin presently works (PHP 7.2, WordPress 5.0), it’s likely to break in the future.