Groupe instructeur selector default blank

app/views/shared/dossiers/_edit.html.haml

@@ -34,19 +34,9 @@
       = f.label :groupe_instructeur_id do
         = dossier.procedure.routing_criteria_name
         %span.mandatory *
-      -# The routing dropdown has 'include_blank: false', because otherwise a blank
-      -# value may nullify the groupe_instructeur – and thus the link between the dossier
-      -# and its procedure.
-      -#
-      -# If, one day, we need to make clearer to the user that they must actually choose an
-      -# option, THINK TWICE before adding a blank option, and what would happen if the form is
-      -# saved when the blank option is selected.
-      -# Instead please consider other possibilities; like using CSS to gray out the default option,
-      -# or adding some "(please select an option)" wording aside the label of the default group.
-      -# CSS
       = f.select :groupe_instructeur_id,
         dossier.procedure.groupe_instructeurs.order(:label).map { |gi| [gi.label, gi.id] },
-        { include_blank: false }
+        { include_blank: dossier.brouillon? }
 
     = f.fields_for :champs, dossier.champs do |champ_form|
       - champ = champ_form.object