Redmine DMSF

Redmine 4.2.2
When a user clicks to accept the workflow step the following error occurs:

Started POST "/dmsf_workflows/2/new_action" for 192.168.3.41 at 2021-08-22 13:38:04 +0000
Processing by DmsfWorkflowsController#new_action as HTML
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"2zQoX/Gn6an8JKx9O/hbD6SYuuL+g2PxM1RPiIs1Fk1RPVTEscAOcJBy6/J0isUp+tXuo4RXRnDwOkLClg9SRg==", "dmsf_workflow_step_assignment_id"=>"5", "dmsf_file_revision_id"=>"4", "step_action"=>"1", "note"=>"I.O.", "user_search"=>"", "commit"=>"OK", "id"=>"2"}
  Current user: kerstin_neumann (id=11)
  Rendering plugins/redmine_dmsf/app/views/dmsf_mailer/workflow_notification.text.erb within layouts/mailer
  Rendered plugins/redmine_dmsf/app/views/dmsf_mailer/workflow_notification.text.erb within layouts/mailer (1.9ms)
  Rendering plugins/redmine_dmsf/app/views/dmsf_mailer/workflow_notification.html.erb within layouts/mailer
  Rendered plugins/redmine_dmsf/app/views/dmsf_mailer/workflow_notification.html.erb within layouts/mailer (0.9ms)
  Rendering plugins/redmine_dmsf/app/views/dmsf_mailer/workflow_notification.text.erb within layouts/mailer
  Rendered plugins/redmine_dmsf/app/views/dmsf_mailer/workflow_notification.text.erb within layouts/mailer (0.3ms)
  Rendering plugins/redmine_dmsf/app/views/dmsf_mailer/workflow_notification.html.erb within layouts/mailer
  Rendered plugins/redmine_dmsf/app/views/dmsf_mailer/workflow_notification.html.erb within layouts/mailer (0.3ms)
Completed 500 Internal Server Error in 197ms (ActiveRecord: 27.4ms)
  
NoMethodError (undefined method `h' for #<DmsfWorkflowsController:0x00007fe634476bd0>):
  
plugins/redmine_dmsf/app/controllers/dmsf_workflows_controller.rb:167:in `block in new_action'
plugins/redmine_dmsf/app/controllers/dmsf_workflows_controller.rb:167:in `collect'
plugins/redmine_dmsf/app/controllers/dmsf_workflows_controller.rb:167:in `new_action'
lib/redmine/sudo_mode.rb:61:in `sudo_mode'
plugins/redmine_dmsf/lib/redmine_dmsf/webdav/custom_middleware.rb:56:in `call'