Subscribe Widget fatal error

Anspress v3a1

[17-Apr-2016 13:16:51 UTC] PHP Fatal error:  Uncaught Error: Call to undefined function is_question_tag() in /home/wp-content/plugins/anspress-question-answer/includes/subscriber.php:353
Stack trace:
#0 /home/wp-content/plugins/anspress-question-answer/widgets/subscribe.php(43): ap_question_subscribers()
#1 /home/wp-includes/class-wp-widget.php(347): AnsPress_Subscribe_Widget->widget(Array, Array)
#2 /home/wp-includes/widgets.php(729): WP_Widget->display_callback(Array, Array)
#3 /home/wp-content/themes/justwrite/sidebar.php(14): dynamic_sidebar(‘main-sidebar’)
#4 /home/wp-includes/template.php(562): require_once(‘/home/t…’)
#5 /home/wp-includes/template.php(521): load_template(‘/home/t…’, true)
#6 /home/wp-includes/general-template.php(125): locate_template(Array, true)