Redmine

I got this error in production log when try to update some issues.

NoMethodError (undefined method `>' for nil:NilClass):
app/models/custom_field.rb:355:in `validate_field_value_format'
app/models/custom_field.rb:334:in `validate_field_value'
app/models/custom_field_value.rb:46:in `validate_value'
lib/plugins/acts_as_customizable/lib/acts_as_customizable.rb:126:in `each'
lib/plugins/acts_as_customizable/lib/acts_as_customizable.rb:126:in `validate_custom_field_values'
app/controllers/issues_controller.rb:470:in `block in save_issue_with_child_records'
app/controllers/issues_controller.rb:458:in `save_issue_with_child_records'
app/controllers/issues_controller.rb:184:in `update'

Redmine 2.4.2.stable
Ruby version: 1.9.3-p484
Rails version: 3.2.16
Database adapter: MySQL

no plugin installed