Undefined index when plugin is installed

[alexanderpublit]

Undefined index: page in /Applications/MAMP/htdocs/pub/wp-content/plugins/slack-integration/inc/plugin.class.php on line 597

Undefined index: page in /Applications/MAMP/htdocs/pub/wp-content/plugins/slack-integration/inc/plugin.class.php on line 603

Undefined index: page in /Applications/MAMP/htdocs/pub/wp-content/plugins/slack-integration/inc/plugin.class.php on line 607

[wormeyman]

The same error message as #30