Unable to save field when updating field to empty

Hi,

I am unable to set a field to empty by removing the content of the field and click on update.

These are the fields.

<?php
add_filter( 'rwmb_meta_boxes', 'your_prefix_register_meta_boxes' );

function your_prefix_register_meta_boxes( $meta_boxes ) {
    $prefix = '';

    $meta_boxes[] = [
        'title'        => esc_html__( 'Endowment Form', 'text-domain' ),
        'id'           => 'endowment-form',
        'post_types'   => ['endowment'],
        'context'      => 'normal',
        'priority'     => 'high',
        'fields'       => [
            [
                'id'   => $prefix . 'title',
                'type' => 'text',
                'name' => esc_html__( 'Title', 'text-domain' ),
            ],
            [
                'id'   => $prefix . 'description',
                'type' => 'textarea',
                'name' => esc_html__( 'Description', 'text-domain' ),
            ],
            [
                'id'   => $prefix . 'content_text',
                'name' => esc_html__( 'Content', 'text-domain' ),
                'type' => 'wysiwyg',
            ],
            [
                'id'   => $prefix . 'icon',
                'type' => 'text',
                'name' => esc_html__( 'Icon', 'text-domain' ),
            ],
            [
                'id'   => $prefix . 'image',
                'type' => 'text',
                'name' => esc_html__( 'Image', 'text-domain' ),
            ],
        ],
        'table'        => 'endowments',
        'storage_type' => 'custom_table',
    ];

    return $meta_boxes;
}

I have also checked that database table field I am editing allows null.

There is also no PHP error.

What else can I check?

Thanks!