wrong document edited in document creation flow

This is a side effect of NXP-5896

To reproduce this problem

• create a document
• while in the creation form, select another language
• after the redirection, a creation form is displayed with the type of the current document.

When selecting the language, the method navigationContext.setChangeableDocument is called with a null argument, then with the changeable.

We want to forbid users to select language when they entered in the document creation flow.