Number Field With Default Value Break in Classic Planning Board

Steps to reproduce:

1. install JIRA 5.1.7 and GreenHopper version 6.0.8
2. create a custom field type Number Field(with Default Value, refer to NF.png)
3. in Classic Planning Board, add the Number Field to the Card Styles . Refer to screenshot CardStyle
4. in Classic Planning Board, create New Card. Number Field will have problem as per shown in the Problem.png . The Number Field will has error:

   $action.getHtmlEncodedText($afield.getDefaultValue($boardIssue))
   

workaround:
Remove the Default Value from the Number Field

This is not affecting GreenHopper 6.0.6, but downgrading to 6.0.6 or below is not recommended . Please also note that, Classic Board will be deprecated soon. Thus, please consider migrating to Rapid Board.