Why?

Fatal error: Uncaught Error: [] operator not supported for strings in /home/u6vw3n5iyjob/public_html/sarah2014/wp-content/themes/brandon/functions/meta-functions.php:1863 Stack trace: #0 /home/u6vw3n5iyjob/public_html/sarah2014/wp-content/themes/brandon/includes/content-single.php(87): mfn_builder_print(7) #1 /home/u6vw3n5iyjob/public_html/sarah2014/wp-includes/template.php(732): require('/home/u6vw3n5iy...') #2 /home/u6vw3n5iyjob/public_html/sarah2014/wp-includes/template.php(676): load_template('/home/u6vw3n5iy...', false, Array) #3 /home/u6vw3n5iyjob/public_html/sarah2014/wp-includes/general-template.php(204): locate_template(Array, true, false, Array) #4 /home/u6vw3n5iyjob/public_html/sarah2014/wp-content/themes/brandon/single.php(22): get_template_part('includes/conten...', 'single') #5 /home/u6vw3n5iyjob/public_html/sarah2014/wp-includes/template-loader.php(106): include('/home/u6vw3n5iy...') #6 /home/u6vw3n5iyjob/public_html/sarah2014/wp-blog-header.php(19): require_once('/home/u6vw3n5iy...') #7 /home/u6vw3n5iyjob/ in /home/u6vw3n5iyjob/public_html/sarah2014/wp-content/themes/brandon/functions/meta-functions.php on line 1863