Make delayed job display_name failsafe

The display_name method is used by delayed job to log information
about a certain job, including failure messages. Whenever a job class
is moved or deleted, the instances still scheduled cannot be
constantized anymore, causing display_name and hence the log method to
raise an exception. In certain cases, e.g. when logging happens in a
rescue block, this may terminate the entire delayed job worker. With
the failsafe method, the worker handles failed jobs gracefully and
continues work, all with appropriate log output.

activejob/lib/active_job/queue_adapters/delayed_job_adapter.rb

@@ -50,6 +50,8 @@ def perform
         private
           def log_arguments?
             job_data["job_class"].constantize.log_arguments?
+          rescue NameError
+            false
           end
       end
     end

activejob/test/cases/delayed_job_adapter_test.rb

@@ -30,4 +30,17 @@ class DelayedJobAdapterTest < ActiveSupport::TestCase
     assert_equal "HelloJob [#{job_id}] from DelayedJob(default) with arguments: #{arguments}",
                  job_wrapper.display_name
   end
+
+  test "shows name for invalid job class" do
+    job_id = SecureRandom.uuid
+
+    job_wrapper = ActiveJob::QueueAdapters::DelayedJobAdapter::JobWrapper.new(
+      "job_class" => "NotExistingJob",
+      "queue_name" => "default",
+      "job_id" => job_id,
+      "arguments" => { "some" => { "job" => "arguments" } }
+    )
+
+    assert_equal "NotExistingJob [#{job_id}] from DelayedJob(default)", job_wrapper.display_name
+  end
 end