WordPress Text Toggle Plugin

Fatal error: Uncaught TypeError: Cannot access offset of type string on string in /home/quickplu/public_html/wp-content/themes/tradesman/functions.php:458 Stack trace: #0 /home/quickplu/public_html/wp-includes/shortcodes.php(355): tradesman_toggle('', '<a href="http:/...', 'toggle') #1 [internal function]: do_shortcode_tag(Array) #2 /home/quickplu/public_html/wp-includes/shortcodes.php(227): preg_replace_callback('/\\[(\\[?)(toggle...', 'do_shortcode_ta...', '<p>There are pl...') #3 /home/quickplu/public_html/wp-includes/class-wp-hook.php(308): do_shortcode('<p>There are pl...') #4 /home/quickplu/public_html/wp-includes/plugin.php(205): WP_Hook->apply_filters('<p>There are pl...', Array) #5 /home/quickplu/public_html/wp-includes/post-template.php(255): apply_filters('the_content', 'There are plent...') #6 /home/quickplu/public_html/wp-content/themes/tradesman/page.php(29): the_content() #7 /home/quickplu/public_html/wp-includes/template-loader.php(106): include('/home/quickplu/...') #8 /home/quickplu/public_html/wp-blog-header.php(19): require_once('/home/quickplu/...') #9 /home/quickplu/public_html/index.php(17): require('/home/quickplu/...') #10 {main} thrown in /home/quickplu/public_html/wp-content/themes/tradesman/functions.php on line 458