Fatal error: Uncaught TypeError: call_user_func_array(): Argument #1 ($callback) must be a valid callback, non-static method OWA_Block::register_widget_sidebar() cannot be called statically in /customers/4/4/b/abp-bvp.be/httpd.www/wp-includes/class-wp-hook.php:307
Stack trace:
#0 /customers/4/4/b/abp-bvp.be/httpd.www/wp-includes/class-wp-hook.php(331): WP_Hook->apply_filters('', Array)
#1 /customers/4/4/b/abp-bvp.be/httpd.www/wp-includes/plugin.php(476): WP_Hook->do_action(Array)
#2 /customers/4/4/b/abp-bvp.be/httpd.www/wp-includes/widgets.php(1854): do_action('widgets_init')
#3 /customers/4/4/b/abp-bvp.be/httpd.www/wp-includes/class-wp-hook.php(307): wp_widgets_init('')
#4 /customers/4/4/b/abp-bvp.be/httpd.www/wp-includes/class-wp-hook.php(331): WP_Hook->apply_filters(NULL, Array)
#5 /customers/4/4/b/abp-bvp.be/httpd.www/wp-includes/plugin.php(476): WP_Hook->do_action(Array)
#6 /customers/4/4/b/abp-bvp.be/httpd.www/wp-settings.php(598): do_action('init')
#7 /customers/4/4/b/abp-bvp.be/httpd.www/wp-config.php(99): require_once('/customers/4/4/...')
#8 /customers/4/4/b/abp-bvp.be/httpd.www/wp-load.php(50): require_once('/customers/4/4/...')
#9 /customers/4/4/b/abp-bvp.be/httpd.www/wp-blog-header.php(13): require_once('/customers/4/4/...')
#10 /customers/4/4/b/abp-bvp.be/httpd.www/index.php(17): require('/customers/4/4/...')
#11 {main}
  thrown in /customers/4/4/b/abp-bvp.be/httpd.www/wp-includes/class-wp-hook.php on line 307