Steps to reproduce:

1. Add the following configuration:

   ibexa_fieldtype_page:
       blocks:
           nested_block:
               name: My Block
               category: default
               thumbnail: /bundles/ibexaicons/img/all-icons.svg#edit
               views:
                   default:
                       name: Default block layout
                       template: '@ibexadesign/blocks/my_block.html.twig'
                       priority: -255
               attributes:
                   picture_gallery:
                       name: Picture
                       type: nested_attribute
                       options:
                           multiple: true
                           help:
                               html: true
                           attributes:
                               lady:
                                   name: lady
                                   type: embed
                                   validators:
                                       not_blank:
                                           message: 'Provide a value'
                                   options:
                                       help:
                                           html: true
                               caption:
                                   name: Caption
                                   type: richtext
                                   options:
                                       help:
                                           html: true
                                           text: 'In case of empty Caption it will render from image Caption'
   

2. Create any Landing Page content and place the configured block.
3. Try to use some style or anything from the Rich Text Editor toolbar inside the "Caption" attribute.

Result:
Rich Text Editor toolbar is not usable. One is getting JS console errors:

ibexa-richtext-onlineeditor-js.js:110746 Uncaught TypeError: Cannot read properties of null (reading 'offsetWidth')

Expected result:
Rich Text Editor toolbar should be working properly.