Fatal error: Uncaught TypeError: call_user_func_array(): Argument #1 ($callback) must be a valid callback, non-static method Document::build() cannot be called statically in /var/www/html/wp-includes/class-wp-hook.php:287 Stack trace: #0 /var/www/html/wp-includes/class-wp-hook.php(311): WP_Hook->apply_filters(NULL, Array) #1 /var/www/html/wp-includes/plugin.php(478): WP_Hook->do_action(Array) #2 /var/www/html/wp-includes/general-template.php(3009): do_action('wp_head') #3 /var/www/html/wp-content/themes/thesis/header.php(9): wp_head() #4 /var/www/html/wp-includes/template.php(730): require_once('/var/www/html/w...') #5 /var/www/html/wp-includes/template.php(676): load_template('/var/www/html/w...', true, Array) #6 /var/www/html/wp-includes/general-template.php(48): locate_template(Array, true, true, Array) #7 /var/www/html/wp-content/themes/thesis/lib/html/frameworks.php(6): get_header() #8 /var/www/html/wp-content/themes/thesis/index.php(1): thesis_html_framework() #9 /var/www/html/wp-includes/template-loader.php(113): include('/var/www/html/w...') #10 /var/www/html/wp-blog-header.php(19): require_once('/var/www/html/w...') #11 /var/www/html/index.php(17): require('/var/www/html/w...') #12 {main} thrown in /var/www/html/wp-includes/class-wp-hook.php on line 287