Cannot create issue after installing Scrumbler 1.5

[Tiennd]

Hi all,

I cannot create new issue with assigning an Target Version after I install Scrumbler 1.5 on Redmine 2.0.2. The error message show:

Internal error

An error occurred on the page you were trying to access.
If you continue to experience problems please contact your Redmine administrator for assistance.

If you are the Redmine administrator, check your log files for details about the error.

The error message logged in log file is as below:

Started POST "/redmine/projects/aa/issues" for 127.0.0.1 at Thu Jul 26 11:18:13 +0700 2012
Processing by IssuesController#create as HTML
Parameters: {"continue"=>"Create and continue", "authenticity_token"=>"23ashKyleIPzA80K3mYRWXutjc6CN+sccs20iH93aAs=", "utf8"=>"✓", "issue"=>{"estimated_hours"=>"", "priority_id"=>"4", "assigned_to_id"=>"1", "parent_issue_id"=>"", "tracker_id"=>"1", "start_date"=>"2012-07-26", "subject"=>"sdfdsfd", "due_date"=>"", "done_ratio"=>"0", "status_id"=>"1", "custom_field_values"=>{"1"=>"4", "2"=>"8"}, "is_private"=>"0", "description"=>"", "fixed_version_id"=>"1"}, "project_id"=>"aa", "attachments"=>{"1"=>{"description"=>""}}}
Completed 500 Internal Server Error in 172ms

NoMethodError (undefined method empty?' for :sprint_not_planning_error:Symbol): app/controllers/issues_controller.rb:148:increate'

The similar error show up when i update issue.

What can I try to fix it.

Thank you in advance.
Tiennd