[Fix #3016] Do not crash if PJ has no extension

spec/uploaders/piece_justificative_uploader_spec.rb

@@ -0,0 +1,14 @@
+require 'spec_helper'
+
+describe PieceJustificativeUploader do
+  let(:pj) { create(:piece_justificative, :rib) }
+
+  it { expect(pj.content.filename).to eq 'piece_justificative.pdf' }
+
+  context 'when extension is nil' do
+    it do
+      expect(pj.content.file).to receive(:extension).and_return(nil)
+      expect(pj.content.filename).to eq 'piece_justificative.'
+    end
+  end
+end