Error using editor plugin on front end

When using using the editor plugin button "Showtime Image Gallery" on the front end using both JCE and Tinymce with error reporting set to default I get a blank white popup,if I set error reporting to maximum I get

Warning: require_once(/xxxxx/administrator/includes/toolbar.php): failed to open stream: No such file or directory in /xxxxx/components/com_showtime/showtime.php on line 22 Fatal error: require_once(): Failed opening required '/xxxxx/administrator/includes/toolbar.php' (include_path='.:/usr/share/pear:/usr/share/php') in /xxxxx/components/com_showtime/showtime.php on line 22

administrator/includes/toolbar.php seems to have been removed and replaced with subtoolbar.php when updating to Joomla 3.9.1, or possibly earlier versions.

As a temporary fix, I uploaded administrator/includes/toolbar.php from an earlier Joomla version and this now works for me.

Please look into this and provide a better solution or update if necessary.

Joomla 3.9.1, PHP 7.1.24, Showtime Image Gallery. 1.3.0

Regards