Fabricación de maquinaria industrial

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 /customers/1/9/7/gruposavia.eu/httpd.www/wp-includes/class-wp-hook.php:310 Stack trace: #0 /customers/1/9/7/gruposavia.eu/httpd.www/wp-includes/plugin.php(205): WP_Hook->apply_filters('karma_walker', Array) #1 /customers/1/9/7/gruposavia.eu/httpd.www/wp-content/themes/karma/framework/karma-megamenu.php(35): apply_filters('karma_mega_menu...', 'karma_walker') #2 /customers/1/9/7/gruposavia.eu/httpd.www/wp-includes/class-wp-hook.php(310): karma_megamenu->modify_arguments(Array) #3 /customers/1/9/7/gruposavia.eu/httpd.www/wp-includes/plugin.php(205): WP_Hook->apply_filters(Array, Array) #4 /customers/1/9/7/gruposavia.eu/httpd.www/wp-includes/nav-menu-template.php(97): apply_filters('wp_nav_menu_arg...', Array) #5 /customers/1/9/7/gruposavia.eu/httpd.www/wp-content/themes/karma/theme-template-part-horizontal-sub-menu.php(38): wp_nav_menu(Array) #6 /customers/1/9/7/gruposavia.eu/httpd.www/wp-includes/template.php(787): require('/customers/1/9/...') #7 /customers/1/9/7/gruposavia.eu/httpd.www/wp-includes/template.php(720): load_template('/customers/1/9/...', false, Array) #8 /customers/1/9/7/gruposavia.eu/httpd.www/wp-includes/general-template.php(206): locate_template(Array, true, false, Array) #9 /customers/1/9/7/gruposavia.eu/httpd.www/wp-content/themes/karma/page.php(204): get_template_part('theme-template-...') #10 /customers/1/9/7/gruposavia.eu/httpd.www/wp-includes/template-loader.php(106): include('/customers/1/9/...') #11 /customers/1/9/7/gruposavia.eu/httpd.www/wp-blog-header.php(19): require_once('/customers/1/9/...') #12 /customers/1/9/7/gruposavia.eu/httpd.www/index.php(17): require('/customers/1/9/...') #13 {main} thrown in /customers/1/9/7/gruposavia.eu/httpd.www/wp-includes/class-wp-hook.php on line 310