Setting Group Picker in post-function after converting issue to sub task

[jeetu]

Hi,Custom group picker field name is active users. the following script works pretty good while creating issue. Main/Parent issue picks project admin and subtask based workflow picks jira-users group automatically according to the script.

import com.atlassian.jira.component.ComponentAccessor
import com.atlassian.jira.issue.CustomFieldManager
import com.atlassian.jira.issue.Issue
import com.atlassian.jira.issue.ModifiedValue
import com.atlassian.jira.issue.util.DefaultIssueChangeHolder
import com.atlassian.jira.issue.util.IssueChangeHolder

//Get Issue Object
Issue issue = issue //The issue object is internally retrieved in the post-function

//Get instance of Custom Field Manager
def customFieldManager = ComponentAccessor.getComponent(CustomFieldManager)

//Initialize variables to setup group picker & automation type custom field value
def groupManager = ComponentAccessor.getGroupManager()
def singleGroupCf = customFieldManager.getCustomFieldObject("customfield_11119")

def group = groupManager.getGroup("Project Admins")// for subtasks based workflow i use her jira-users//
List groupList = new ArrayList()
groupList.add(group)
IssueChangeHolder changeHolder = new DefaultIssueChangeHolder();
singleGroupCf.updateValue(null, issue, new ModifiedValue(issue.getCustomFieldValue(singleGroupCf), groupList), changeHolder)
issue.store()

But its not working while converting issue into subtask. I mean the custom group picker field is not picking jira-users group automatically.if anyone,can give a solution for me ,it would be helpful