Fix save on auto save of resources (messages, widget templates...)

Steps to reproduce:

• upload a messages file in the Resources tab
• using the online editor, make changes to it
• do not save and navigate elsewhere
• the "save changes or discard" popup is shown
• hit "save"
  ==> the save is not really triggered, navigation is not effective, and when trying to navigate elsewhere again, the "save changes or discard" popup appears again

the same problem is visible on sinilar editors (when editing a xhtml widget template for instance)