Fatal error: Uncaught TypeError: Unsupported operand types: string - int in /home/muungwan/public_html/wp-content/plugins/nd-learning/inc/functions/functions.php:42 Stack trace: #0 /home/muungwan/public_html/wp-content/plugins/nd-learning/addons/visualcomposer/courses/layout/layout-9.php(125): nd_learning_get_course_availability(1693) #1 /home/muungwan/public_html/wp-content/plugins/nd-learning/addons/visualcomposer/courses/index.php(60): include('/home/muungwan/...') #2 /home/muungwan/public_html/wp-includes/shortcodes.php(434): nd_learning_vc_shortcode_courses(Array, '', 'nd_learning_cou...') #3 [internal function]: do_shortcode_tag(Array) #4 /home/muungwan/public_html/wp-includes/shortcodes.php(273): preg_replace_callback('/\\[(\\[?)(nd_lea...', 'do_shortcode_ta...', '[nd_learning_co...') #5 /home/muungwan/public_html/wp-content/plugins/nd-learning/addons/related-course/index.php(29): do_shortcode('[nd_learning_co...') #6 /home/muungwan/public_html/wp-includes/class-wp-hook.php(324): nd_learning_single_course_related_products('') #7 /home/muungwan/public_html/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters('', Array) #8 /home/muungwan/public_html/wp-includes/plugin.php(517): WP_Hook->do_action(Array) #9 /home/muungwan/public_html/wp-content/plugins/nd-learning/templates/single-course.php(842): do_action('nd_learning_sin...') #10 /home/muungwan/public_html/wp-includes/template-loader.php(106): include('/home/muungwan/...') #11 /home/muungwan/public_html/wp-blog-header.php(19): require_once('/home/muungwan/...') #12 /home/muungwan/public_html/index.php(17): require('/home/muungwan/...') #13 {main} thrown in /home/muungwan/public_html/wp-content/plugins/nd-learning/inc/functions/functions.php on line 42