Fatal error: Undefined constant “FIVESTERDEBUG__”

The latest current release, version 1.5 is causing a fatal error:

Fatal error: Uncaught Error: Undefined constant "FIVESTERDEBUG__" in /var/www/example.com/web/wp-content/plugins/5-sterrenspecialist/5sterrenspecialist.php:153 Stack trace: #0 /var/www/example.com/web/wp-content/plugins/5-sterrenspecialist/5sterrenspecialist.php(192): FiveSter::writeDebug() #1 /var/www/example.com/web/wp-content/plugins/5-sterrenspecialist/5sterrenspecialist.php(132): FiveSter::callAPI() #2 /var/www/example.com/web/wp-includes/shortcodes.php(434): FiveSter->fivesterrenspecialist_shortcode() #3 [internal function]: do_shortcode_tag() #4 /var/www/example.com/web/wp-includes/shortcodes.php(273): preg_replace_callback() #5 /var/www/example.com/web/wp-includes/class-wp-hook.php(326): do_shortcode() #6 /var/www/example.com/web/wp-includes/plugin.php(205): WP_Hook->apply_filters() #7 /var/www/example.com/web/wp-content/plugins/fusion-builder/shortcodes/fusion-text.php(151): apply_filters() #8 /var/www/example.com/web/wp-includes/shortcodes.php(434): FusionSC_FusionText->render() #9 [internal function]: do_shortcode_tag() #10 /var/www/example.com/web/wp-includes/shortcodes.php(273): preg_replace_callback() #11 /var/www/example.com/web/wp-content/plugins/fusion-builder/inc/class-fusion-column-element.php(588): do_shortcode() #12 /var/www/example.com/web/wp-includes/shortcodes.php(434): Fusion_Column_Element->render() #13 [internal function]: do_shortcode_tag() #14 /var/www/example.com/web/wp-includes/shortcodes.php(273): preg_replace_callback() #15 /var/www/example.com/web/wp-content/plugins/fusion-builder/inc/class-fusion-row-element.php(123): do_shortcode() #16 /var/www/example.com/web/wp-includes/shortcodes.php(434): Fusion_Row_Element->render() #17 [internal function]: do_shortcode_tag() #18 /var/www/example.com/web/wp-includes/shortcodes.php(273): preg_replace_callback() #19 /var/www/example.com/web/wp-content/plugins/fusion-builder/shortcodes/fusion-container.php(1095): do_shortcode() #20 /var/www/example.com/web/wp-includes/shortcodes.php(434): FusionSC_Container->render() #21 [internal function]: do_shortcode_tag() #22 /var/www/example.com/web/wp-includes/shortcodes.php(273): preg_replace_callback() #23 /var/www/example.com/web/wp-includes/class-wp-hook.php(324): do_shortcode() #24 /var/www/example.com/web/wp-includes/plugin.php(205): WP_Hook->apply_filters() #25 /var/www/example.com/web/wp-content/plugins/fusion-builder/inc/class-fusion-template-builder.php(1554): apply_filters() #26 /var/www/example.com/web/wp-content/plugins/fusion-builder/inc/class-fusion-template-builder.php(1122): Fusion_Template_Builder->render_content() #27 /var/www/example.com/web/wp-includes/class-wp-hook.php(324): Fusion_Template_Builder->{closure}() #28 /var/www/example.com/web/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters() #29 /var/www/example.com/web/wp-includes/plugin.php(517): WP_Hook->do_action() #30 /var/www/example.com/web/wp-content/themes/Avada/header.php(55): do_action() #31 /var/www/example.com/web/wp-includes/template.php(810): require_once('...') #32 /var/www/example.com/web/wp-includes/template.php(745): load_template() #33 /var/www/example.com/web/wp-includes/general-template.php(48): locate_template() #34 /var/www/example.com/web/wp-content/themes/Avada/100-width.php(15): get_header() #35 /var/www/example.com/web/wp-includes/template-loader.php(106): include('...') #36 /var/www/example.com/web/wp-blog-header.php(19): require_once('...') #37 /var/www/example.com/web/index.php(17): require('...') #38 {main} thrown in /var/www/example.com/web/wp-content/plugins/5-sterrenspecialist/5sterrenspecialist.php on line 153