text: Title: Ckeditor <TypeError: Cannot convert undefined or null to object>
  Body: ### Checklist
  
  - [X] The bug is reproducible against the latest release or `master`.
  - [X] There are no similar issues or pull requests to fix it yet.
  
  ### Describe the bug
  
  Following the guide [sqladmin ckeditor](https://aminalaee.dev/sqladmin/cookbook/using_wysiwyg/) got an error:
  
  ```
  TypeError: Cannot convert undefined or null to object
      at Function.keys (<anonymous>)
      at ou.init (datacontroller.ts:344:42)
      at ou.<anonymous> (observablemixin.ts:277:33)
      at ou.fire (emittermixin.ts:241:31)
      at <computed> [as init] (observablemixin.ts:281:17)
      at classiceditor.ts:227:31
  ```
  
  
  
  ### Steps to reproduce the bug
  
  Follow the ckeditor embedding documentation
  
  ### Expected behavior
  
  _No response_
  
  ### Actual behavior
  
  ```
  TypeError: Cannot convert undefined or null to object
      at Function.keys (<anonymous>)
      at ou.init (datacontroller.ts:344:42)
      at ou.<anonymous> (observablemixin.ts:277:33)
      at ou.fire (emittermixin.ts:241:31)
      at <computed> [as init] (observablemixin.ts:281:17)
      at classiceditor.ts:227:31
  ```
  
  ### Debugging material
  
  _No response_
  
  ### Environment
  
  Sqladmin 0.17.0
  
  ### Additional context
  
  Everything starts working fine if you add the following code 
  
  ```
  <script src="https://cdn.ckeditor.com/ckeditor5/39.0.1/classic/ckeditor.js"></script>
  <script>
      ClassicEditor
          .create(document.querySelector('#content'))
          .catch(error => {
              console.error(error);
          });
  </script>
  ```
  straight into the editor.html template before the last closing block, however I don't think this is the correct behavior.