[TYPO3-english] Workspaces: From draft to live: a file is deleted

[Iban]

Hello,

I'm working with TYPO3 6.1.8 and I see a strange behavior when I work 
with workspaces:

  * As "editor", in "draft", I create a new item in Storage Folder of my
    custom item.
  * My custom item has a field named "img" with this config:

     'exclude' => 0,
     'label' => 'test',
     'config' => array(
         'type' => 'group',
          'internal_type' => 'file',
           'uploadfolder' => 'uploads/tx_myExtension',
                                 'show_thumbs' => 1,
                                 'size' => 5,
                                 'allowed' => 
$GLOBALS['TYPO3_CONF_VARS']['GFX']['imagefile_ext'],
                                 'disallowed' => '',
            )

  * I send my changes to "review" status.
  * When the administrator accepts the changes, the file is deleted
    physically from 'uploads/tx_myExtension' and I don't understand why...

Could you help me?
Thank you so much!