Error with query

In PHP 8.3 if you call

$query->set( 'tax_query', array(
    array(
        'taxonomy' => 'product_cat',
        'operator' => 'EXISTS',
    )
) );

Undefined array key 0+
anything-order-by-terms/modules/base/class.php:298

Undefined property: WP_Error::$slug+
app/plugins/anything-order-by-terms/modules/base/class.php:300

Solution is add check in modules/base/class.php before
if ( ‘term_id’ === $tax_query[‘field’] ) {

if ( !isset( $tax_query['terms'][0] ) )
    return '';

if ( 'term_id' === $tax_query['field'] ) {