Handle nil value for fixity_last_success_date in fixity dashboard

fixes #897

app/helpers/fixity_dashboard_helper.rb

@@ -0,0 +1,6 @@
+# frozen_string_literal: true
+module FixityDashboardHelper
+  def format_fixity_success_date(date)
+    date.nil? ? 'in progress' : date.strftime("%m/%d/%y %I:%M:%S %p %Z")
+  end
+end

app/views/fixity_dashboard/_fixity_table.html.erb

@@ -15,7 +15,7 @@
         <td><%= link_to resource.parent.title.first, Valhalla::ContextualPath.new(child: resource.parent).show %></td>
         <td><%= resource.original_file.fixity_success == 0 ? "failed" : "succeeded" %></td>
         <td><%= resource.updated_at %></td>
-        <td><%= resource.original_file.fixity_last_success_date.strftime("%m/%d/%y %I:%M:%S %p %Z") %></td>
+        <td><%= format_fixity_success_date(resource.original_file.fixity_last_success_date) %></td>
       </tr>
     <% end %>
   </tbody>

spec/helpers/fixity_dashboard_helper_spec.rb

@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+require 'rails_helper'
+
+RSpec.describe FixityDashboardHelper do
+  describe '#format_fixity_success_date' do
+    it 'formats the date as expected' do
+      expect(helper.format_fixity_success_date(nil)).to eq 'in progress'
+      time = Time.current
+      expect(helper.format_fixity_success_date(time)).to eq time.strftime("%m/%d/%y %I:%M:%S %p %Z")
+    end
+  end
+end