Undefined index: length

Hola,

estoy usando el tema oceanwp y elementor, y al ir a usar woolentor para poner los productos el slider query monitor empieza a detectarme 8 errores de php procedentes de este complemento:

wp-content/plugins/woolentor-addons/includes/addons/wl_category.php:425
Elementor\WL_Category_List_Element->render()
wp-content/plugins/elementor/includes/base/controls-stack.php:1892
Elementor\Controls_Stack->render_by_mode()
wp-content/plugins/elementor/includes/base/widget-base.php:549
Elementor\Widget_Base->render_content()
wp-content/plugins/elementor/includes/base/widget-base.php:679
Elementor\Widget_Base->print_content()
wp-content/plugins/elementor/includes/base/element-base.php:650
Elementor\Element_Base->print_element()
wp-content/plugins/elementor/includes/base/element-base.php:911
Elementor\Element_Base->print_content()
wp-content/plugins/elementor/includes/base/element-base.php:650
Elementor\Element_Base->print_element()
wp-content/plugins/elementor/includes/base/element-base.php:911
Elementor\Element_Base->print_content()
wp-content/plugins/elementor/includes/base/element-base.php:650
Elementor\Element_Base->print_element()
wp-content/plugins/elementor/core/base/document.php:1305
Elementor\C\B\Document->print_elements()
wp-content/plugins/elementor/core/base/document.php:942
Elementor\C\B\Document->print_elements_with_wrapper()
wp-content/plugins/elementor/includes/frontend.php:982
Elementor\Frontend->get_builder_content()
wp-content/plugins/elementor/includes/frontend.php:896
Elementor\Frontend->apply_builder_in_content()
wp-includes/class-wp-hook.php:292
apply_filters('the_content')
wp-includes/post-template.php:253
the_content()
wp-content/themes/oceanwp/partials/page/article.php:20
load_template('wp-content/themes/oceanwp/partials/page/article.php')
wp-includes/template.php:676
locate_template()
wp-includes/general-template.php:204
get_template_part('partials/page/article')
wp-content/themes/oceanwp/partials/page/layout.php:20
load_template('wp-content/themes/oceanwp/partials/page/layout.php')
wp-includes/template.php:676
locate_template()
wp-includes/general-template.php:204
get_template_part('partials/page/layout')
wp-content/themes/oceanwp/page.php:36

The page I need help with: [log in to see the link]