How to create Subtask with required fields using Built-in scripts>Create subtask

[Jan Kurowski]

All I get is: 
Error map: [{customfield_11045=Grupa akceptujących is required.}]

Built-in scripts Create subtask fails on required fields

I try to debug using this log as a second line of code in field "Additional issue actions" but it doesn't appear in logs - as if it fails to create subtask before trying to do my code: 

import com.atlassian.jira.component.ComponentAccessor
log.error("************************test*******************")
def cf = customFieldManager.getCustomFieldObject('customfield_11045')

//getting an Option object

def fieldConfig = cf.getRelevantConfig(issue)
def value = ComponentAccessor.optionsManager.getOptions(fieldConfig)?.find { it.toString() == 'Name of group' }
issue.setCustomFieldValue(cf, value)