Fatal error: Uncaught TypeError: call_user_func_array(): Argument #1 ($callback) must be a valid callback, function "sub_nav_walker" not found or invalid function name in /var/www/virtual/colegioelplanet.com/htdocs/wp-includes/class-wp-hook.php:308 Stack trace: #0 /var/www/virtual/colegioelplanet.com/htdocs/wp-includes/plugin.php(205): WP_Hook->apply_filters() #1 /var/www/virtual/colegioelplanet.com/htdocs/wp-content/themes/karma/framework/karma-megamenu.php(35): apply_filters() #2 /var/www/virtual/colegioelplanet.com/htdocs/wp-includes/class-wp-hook.php(308): karma_megamenu->modify_arguments() #3 /var/www/virtual/colegioelplanet.com/htdocs/wp-includes/plugin.php(205): WP_Hook->apply_filters() #4 /var/www/virtual/colegioelplanet.com/htdocs/wp-includes/nav-menu-template.php(97): apply_filters() #5 /var/www/virtual/colegioelplanet.com/htdocs/wp-content/themes/karma/theme-template-part-horizontal-sub-menu.php(38): wp_nav_menu() #6 /var/www/virtual/colegioelplanet.com/htdocs/wp-includes/template.php(785): require('...') #7 /var/www/virtual/colegioelplanet.com/htdocs/wp-includes/template.php(718): load_template() #8 /var/www/virtual/colegioelplanet.com/htdocs/wp-includes/general-template.php(204): locate_template() #9 /var/www/virtual/colegioelplanet.com/htdocs/wp-content/themes/karma/template-full-width.php(10): get_template_part() #10 /var/www/virtual/colegioelplanet.com/htdocs/wp-includes/template-loader.php(106): include('...') #11 /var/www/virtual/colegioelplanet.com/htdocs/wp-blog-header.php(19): require_once('...') #12 /var/www/virtual/colegioelplanet.com/htdocs/index.php(17): require('...') #13 {main} thrown in /var/www/virtual/colegioelplanet.com/htdocs/wp-includes/class-wp-hook.php on line 308