Fix loss of complex widgets when navigating to subwidgets edition page

When editing a complex metadata subwidget, following the link "Go back to previous page" looses all the modifications of the layout (creation, edit, view...) that have not been saved before the widget edition.

Note : this is only a display problem, as navigating to another feature, and coming back to the page, the complex widget appears as saved.

Steps to reproduce:

• define a complex field
• in the document creation page, add the complex widget for this field without saving
• navigate to the subwidgets edition page
• use the "back" link to go back to the layout edition page
  => the newly added complex widget is not displayed anymore