Fatal error: Uncaught TypeError: array_merge(): Argument #3 must be of type array, null given in /customers/d/f/7/zelfverwonding.be/httpd.www/wp-includes/widgets.php:1342
Stack trace:
#0 /customers/d/f/7/zelfverwonding.be/httpd.www/wp-includes/widgets.php(1342): array_merge(Array, Array, NULL)
#1 /customers/d/f/7/zelfverwonding.be/httpd.www/wp-includes/widgets.php(1287): retrieve_widgets(true)
#2 /customers/d/f/7/zelfverwonding.be/httpd.www/wp-includes/class-wp-hook.php(310): _wp_sidebars_changed('Twenty Thirteen')
#3 /customers/d/f/7/zelfverwonding.be/httpd.www/wp-includes/class-wp-hook.php(332): WP_Hook->apply_filters(NULL, Array)
#4 /customers/d/f/7/zelfverwonding.be/httpd.www/wp-includes/plugin.php(517): WP_Hook->do_action(Array)
#5 /customers/d/f/7/zelfverwonding.be/httpd.www/wp-includes/theme.php(3401): do_action('after_switch_th...', 'Twenty Thirteen', Object(WP_Theme))
#6 /customers/d/f/7/zelfverwonding.be/httpd.www/wp-includes/class-wp-hook.php(308): check_theme_switched('')
#7 /customers/d/f/7/zelfverwonding.be/httpd.www/wp-includes/class-wp-hook.php(332): WP_Hook->apply_filters(NULL, Array)
#8 /customers/d/f/7/zelfverwonding.be/httpd.www/wp-includes/plugin.php(517): WP_Hook->do_action(Array)
#9 /customers/d/f/7/zelfverwonding.be/httpd.www/wp-settings.php(623): do_action('init')
#10 /customers/d/f/7/zelfverwonding.be/httpd.www/wp-config.php(96): require_once('/customers/d/f/...')
#11 /customers/d/f/7/zelfverwonding.be/httpd.www/wp-load.php(50): require_once('/customers/d/f/...')
#12 /customers/d/f/7/zelfverwonding.be/httpd.www/wp-blog-header.php(13): require_once('/customers/d/f/...')
#13 /customers/d/f/7/zelfverwonding.be/httpd.www/index.php(17): require('/customers/d/f/...')
#14 {main}
  thrown in /customers/d/f/7/zelfverwonding.be/httpd.www/wp-includes/widgets.php on line 1342