procedure: ignore bad data when computing usual_instruction_time

Fix #3655

app/models/procedure.rb

@@ -467,6 +467,7 @@ class Procedure < ApplicationRecord
 
   def percentile_time(start_attribute, end_attribute, p)
     times = dossiers
+      .where.not(start_attribute => nil, end_attribute => nil)
       .where(end_attribute => 1.month.ago..Time.zone.now)
       .pluck(start_attribute, end_attribute)
       .map { |(start_date, end_date)| end_date - start_date }

spec/models/procedure_spec.rb

@@ -780,6 +780,15 @@ describe Procedure do
       end
     end
 
+    context 'when there is a dossier with bad data' do
+      let(:delays) { [2.days, 2.days] }
+      let!(:bad_dossier) { create_dossier(instruction_date: nil, processed_date: 10.days.ago) }
+
+      it 'ignores bad dossiers' do
+        expect(procedure.usual_instruction_time).to be_within(10.seconds).of(2.days)
+      end
+    end
+
     context 'when there is only one processed dossier' do
       let(:delays) { [1.day] }
       it { expect(procedure.usual_instruction_time).to be_within(10.seconds).of(1.day) }