Checkbox 'Select all' for PM doesn't work in administration mode

Pre-conditions
User has admin permission for JCommune. User has several messages at Outbox page.

Steps to reproduce:

1. Go to messages: Outbox page
2. Enter the administration mode (Click Administartion => Administration mode)
3. Click on first checkbox situated at upper left corner on black field.

Actual result: Nothing happened

Expected result: All checkboxes should be selected

Note, the same is reproduced for Drafts and Inbox pages.