Upload&Edit dialog is in background when access within ck-editor

Steps to reproduce

(you can use the custom-config.txt file as the configuration pointed to configJsFile property in order to create the use-case)

1. use a component with CKEditor and use the image Button/plugin to choose or even edit a selected image into the editor (screenshot_1.png)
   (you can just open a dialog like the following):

   form:
     properties:
       richText:
         label: Text editor
         class: info.magnolia.dam.app.field.DamRichTextFieldDefinition
         configJsFile: /.resources/ckeditor/custom-config.js                           #this config is the one attached in the ticket at custom-config.txt
   

2. Click on the Browse server button to upen the image choose dialog (screenshot_2)
3. Click on the Upload&Edit button to upload a new asset (screenshot_3)
4. The upload&edit dialog window is placed behind the CKE window and can not be access. (screenshot_4)

.. Logs, screenshots, gifs...

Expected results

The upload&edit dialog window is placed in front of the CKE window and can be access.

.. Justify non-trivial expectations with a link to a doc or a relevant discussion.

Actual results

The upload&edit dialog window is placed behind the CKE window and can not be access.

Workaround

Development notes