don't clean the rna champ value

Cleaning the value is useless, when fetching the association,
as the value will be re-written by the dossier update, when the user
fills in the dossier.

Furthermore we need the value to persist when prefilling the champ.

app/models/concerns/rna_champ_association_fetchable_concern.rb

@@ -6,7 +6,9 @@ module RNAChampAssociationFetchableConcern
     update!(data: data, value: rna)
     nil
   rescue APIEntreprise::API::Error, ActiveRecord::RecordInvalid => error
-    update(data: nil, value: nil)
+    self.data = nil
+    self.value = rna
+    save(validate: false)
     if error.try(:network_error?) && !APIEntrepriseService.api_up?
       :network_error
     else