Fix csv export with no dossiers

app/models/procedure.rb

@@ -134,9 +134,7 @@ class Procedure < ActiveRecord::Base
     exportable_dossiers = dossiers.downloadable
 
     headers = exportable_dossiers.any? ? exportable_dossiers.first.export_headers : []
-    data = exportable_dossiers.map do |dossier|
-      dossier.full_data_strings_array
-    end
+    data = exportable_dossiers.any? ? exportable_dossiers.map { |d| d.full_data_strings_array } : [[]]
 
     {
       headers: headers,

spec/models/procedure_spec.rb

@@ -261,11 +261,15 @@ describe Procedure do
     let(:procedure) { create :procedure }
     subject { procedure.generate_export }
 
-    context 'when there are no dossiers' do
-      it { expect(subject[:data]).to eq([]) }
+    shared_examples "export is empty" do
+      it { expect(subject[:data]).to eq([[]]) }
       it { expect(subject[:headers]).to eq([]) }
     end
 
+    context 'when there are no dossiers' do
+      it_behaves_like "export is empty"
+    end
+
     context 'when there are some dossiers' do
       let!(:dossier){ create(:dossier, procedure: procedure, state: 'initiated') }
       let!(:dossier2){ create(:dossier, procedure: procedure, state: 'closed') }
@@ -277,8 +281,7 @@ describe Procedure do
     context 'when there is a draft dossier' do
       let!(:dossier_not_exportable){ create(:dossier, procedure: procedure, state: 'draft') }
 
-      it { expect(subject[:data]).to eq([]) }
-      it { expect(subject[:headers]).to eq([]) }
+      it_behaves_like "export is empty"
     end
   end
 end