Redmine

hi.
When creating a version, i got internal error from gantt chart page.

Environment:
Redmine version 3.3.2
Ruby version 2.0.0-p195
Rails version 4.2.7.1
MySQL 5.1.73
Redmine plugins:
checkList

 Started GET "/projects/pgs/issues/gantt" for 10.192.6.2 at 2017-05-11 15:31:22 +0900
Processing by GanttsController#show as HTML
  Parameters: {"project_id"=>"pgs"}
  Current user: io2oi (id=26)
  Rendered queries/_filters.html.erb (4.4ms)
  Rendered gantts/show.html.erb within layouts/base (23.9ms)
Completed 500 Internal Server Error in 123ms (ActiveRecord: 92.9ms)

ActionView::Template::Error (comparison of BigDecimal with Date failed):
    107: 
    108:   # Width of the entire chart
    109:   g_width = ((@gantt.date_to - @gantt.date_from + 1) * zoom).to_i
    110:   @gantt.render(:top => headers_height + 8,
    111:                 :zoom => zoom,
    112:                 :g_width => g_width,
    113:                 :subject_width => subject_width)
  app/models/project.rb:622:in `each'
  app/models/project.rb:622:in `max'
  app/models/project.rb:622:in `due_date'
  app/models/project.rb:626:in `overdue?'
  lib/redmine/helpers/gantt.rb:690:in `html_subject_content'
  lib/redmine/helpers/gantt.rb:699:in `html_subject'
  lib/redmine/helpers/gantt.rb:324:in `subject'
  lib/redmine/helpers/gantt.rb:286:in `subject_for_project'
  lib/redmine/helpers/gantt.rb:257:in `render_object_row'
  lib/redmine/helpers/gantt.rb:216:in `render_project'
  lib/redmine/helpers/gantt.rb:205:in `block in render'
  app/models/project.rb:817:in `block in project_tree'
  app/models/project.rb:813:in `each'
  app/models/project.rb:813:in `project_tree'
  lib/redmine/helpers/gantt.rb:203:in `render'
  app/views/gantts/show.html.erb:110:in `_app_views_gantts_show_html_erb__1744740460631428250_70172295825500'
  app/controllers/gantts_controller.rb:43:in `block (2 levels) in show'
  app/controllers/gantts_controller.rb:42:in `show'
  lib/redmine/sudo_mode.rb:63:in `sudo_mode'

Why does this error occur?

Please also let me know how you can solve this problem.