error in the login widget

Hello,
i write because in the login widget there is this error:

Fatal error: Uncaught Error: Call to a member function tabs_active() on null in /home/timetoda/public_html/wp-content/plugins/login-widget-for-ultimate-member/templates/login-widget/login-view.php:37 Stack trace: #0 /home/timetoda/public_html/wp-content/plugins/login-widget-for-ultimate-member/um-login-widget.php(118): include() #1 /home/timetoda/public_html/wp-content/plugins/login-widget-for-ultimate-member/um-login-widget.php(69): UM_Login_Widget->load_template(‘login-widget/lo…’, Array) #2 /home/timetoda/public_html/wp-includes/class-wp-widget.php(372): UM_Login_Widget->widget(Array, Array) #3 /home/timetoda/public_html/wp-includes/widgets.php(742): WP_Widget->display_callback(Array, Array) #4 /home/timetoda/public_html/wp-content/themes/edge/sidebar.php(31): dynamic_sidebar(‘edge_main_sideb…’) #5 /home/timetoda/public_html/wp-includes/template.php(688): require_once(‘/home/timetoda/…’) #6 /home/timetoda/public_html/wp-includes/template.php(647): load_template(‘/home/timetoda/…’, true) #7 /home/timetoda/public in /home/timetoda/public_html/wp-content/plugins/login-widget-for-ultimate-member/templates/login-widget/login-view.php on line 37

Why ?
Thank you very much
Giulia