Redmine

Hi, I have the same issue as described in #17370 which had been closed without any answer. I think it's a bug, that's why I describe it with some logs.
When I try to create an issue by filling every fields except parent, redmine warns me that the default parent task 0 is invalid.
If I empty the parent field and repost the form I got a 404 error with this server log :

Started GET "/projects/testproj/issues/new" for 127.0.0.1 at 2014-10-08 10:59:18 +0200
Processing by IssuesController#new as HTML
  Parameters: {"project_id"=>"testproj"}
  Current user: dev(id=2)
  Rendered issues/_form_custom_fields.html.erb (31.0ms)
  Rendered issues/_attributes.html.erb (156.0ms)
  Rendered issues/_form.html.erb (234.0ms)
  Rendered attachments/_form.html.erb (16.0ms)
  Rendered issues/new.html.erb within layouts/base (250.0ms)
Completed 200 OK in 484.0ms (Views: 218.0ms | ActiveRecord: 155.0ms)
Started POST "/projects/testproj/issues" for 127.0.0.1 at 2014-10-08 10:59:58 +0200
Processing by IssuesController#create as HTML
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"0ELxq1yuzmkfrTze8a/AvCOPND542Hk946rJkEnmHy8=", "issue"=>{"is_private"=>"1", "tracker_id"=>"1", "subject"=>"z", "description"=>"z", "status_id"=>"1", "priority_id"=>"2", "assigned_to_id"=>"", "fixed_version_id"=>"6", "parent_issue_id"=>"", "start_date"=>"2014-10-08", "due_date"=>"2014-10-08", "estimated_hours"=>"8", "done_ratio"=>"0"}, "commit"=>"Créer", "project_id"=>"testproj"}
  Current user: dev(id=2)
  Rendered mailer/_issue.text.erb (16.0ms)
  Rendered mailer/issue_add.text.erb within layouts/mailer (16.0ms)
  Rendered mailer/_issue.html.erb (0.0ms)
  Rendered mailer/issue_add.html.erb within layouts/mailer (16.0ms)
Completed 404 Not Found in 1500.0ms

ActiveRecord::RecordNotFound (Couldn't find Issue without an ID):
  lib/plugins/awesome_nested_set/lib/awesome_nested_set/awesome_nested_set.rb:497:in `move_to'
  lib/plugins/awesome_nested_set/lib/awesome_nested_set/awesome_nested_set.rb:426:in `in_tenacious_transaction'
  lib/plugins/awesome_nested_set/lib/awesome_nested_set/awesome_nested_set.rb:492:in `move_to'
  lib/plugins/awesome_nested_set/lib/awesome_nested_set/awesome_nested_set.rb:491:in `move_to'
  lib/plugins/awesome_nested_set/lib/awesome_nested_set/awesome_nested_set.rb:356:in `move_to_right_of'
  app/models/issue.rb:1309:in `update_nested_set_attributes_on_parent_change'
  app/models/issue.rb:1294:in `update_nested_set_attributes'
  app/models/issue.rb:165:in `create_or_update'
  app/controllers/issues_controller.rb:146:in `create'