PHP error

I’m getting the following errors in my log file. The plug in seems to be working fine however. Any thoughts on whats causing this?

[Tue Sep 04 08:38:01.280131 2018] [php7:warn] [pid 1288:tid 1324] [client 192.168.0.8:50352] PHP Warning: Use of undefined constant pt_splitter_widget – assumed ‘pt_splitter_widget’ (this will throw an Error in a future version of PHP) in C:\\Apache24\\htdocs\\secure\\wp\\wp-content\\plugins\\page-title-splitter\\pts.php on line 477, referer: https://gioculinarystudio.com/wp/wp-admin/post.php?post=11541&action=edit
[Tue Sep 04 08:38:01.859428 2018] [php7:warn] [pid 1288:tid 1072] [client 24.213.249.66:54424] PHP Warning: Use of undefined constant pt_splitter_widget – assumed ‘pt_splitter_widget’ (this will throw an Error in a future version of PHP) in C:\\Apache24\\htdocs\\secure\\wp\\wp-content\\plugins\\page-title-splitter\\pts.php on line 477, referer: https://gioculinarystudio.com/wp/wp-cron.php?doing_wp_cron=1536064681.5401320457458496093750
[Tue Sep 04 08:38:21.353491 2018] [php7:warn] [pid 1288:tid 1324] [client 69.162.124.228:47516] PHP Warning: Use of undefined constant pt_splitter_widget – assumed ‘pt_splitter_widget’ (this will throw an Error in a future version of PHP) in C:\\Apache24\\htdocs\\secure\\wp\\wp-content\\plugins\\page-title-splitter\\pts.php on line 477, referer: http://gioculinarystudio.com
[Tue Sep 04 08:38:21.788249 2018] [php7:warn] [pid 1288:tid 1072] [client 24.213.249.66:54452] PHP Warning: Use of undefined constant pt_splitter_widget – assumed ‘pt_splitter_widget’ (this will throw an Error in a future version of PHP) in C:\\Apache24\\htdocs\\secure\\wp\\wp-content\\plugins\\page-title-splitter\\pts.php on line 477, referer: https://gioculinarystudio.com/wp/wp-cron.php?doing_wp_cron=1536064701.4753859043121337890625

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