500 internal error

I have a 500 internal error on the pages containing an event-list shortcode.
I have got to disable the plugin

wordpress is 4.9.4
event list plugin is 0.8.1
php version is 7.0

setting debug mode, here is the error:

Notice: Undefined property: SC_Event_List::$categories in /home/folder/websitefolder/wp-content/plugins/event-list/includes/sc_event-list.php on line 232

Fatal error: Uncaught Error: Call to a member function convert_db_string() on null in /home/folder/websitefolder/wp-content/plugins/event-list/includes/sc_event-list.php:232 Stack trace: #0 /home/folder/websitefolder/wp-content/plugins/event-list/includes/sc_event-list.php(176): SC_Event_List->html_event(Object(EL_Event), Array, true) #1 /home/folder/websitefolder/wp-content/plugins/event-list/includes/sc_event-list.php(124): SC_Event_List->html_events(Array) #2 /home/folder/websitefolder/wp-content/plugins/event-list/event-list.php(105): SC_Event_List->show_html(Array) #3 /home/folder/websitefolder/wp-includes/shortcodes.php(319): Event_List->shortcode_event_list(Array, ”, ‘event-list’) #4 [internal function]: do_shortcode_tag(Array) #5 /home/folder/websitefolder/wp-includes/shortcodes.php(197): preg_replace_callback(‘/\\[(\\[?)(event\\…’, ‘do_shortcode_ta…’, ‘<h1>Appuntament…’) #6 /home/folder/websitefolder/wp-conten in /home/folder/websitefolder/wp-content/plugins/event-list/includes/sc_event-list.php on line 232

Thank you!