Which line causes a null pointer exception in Jira automation rule?

I am using a Jira automation rule and I would like to know which line is causing this nullpointer exception.

I am getting an error message saying that I have a null pointer exception but no indication on which one. How is it possible to know exactly which line is causing this nullpointer exception?

Here is my code: 

package SuperFeature

import com.atlassian.jira.bc.project.component.ProjectComponent

import com.atlassian.jira.issue.fields.CustomField

import com.atlassian.jira.issue.Issue

import org.apache.log4j.Logger

import com.atlassian.jira.component.ComponentAccessor

import com.atlassian.jira.issue.IssueManager

import com.atlassian.jira.util.ImportUtils

import com.atlassian.jira.issue.CustomFieldManager

import com.atlassian.jira.issue.MutableIssue

import com.atlassian.jira.issue.index.IssueIndexManager

import com.atlassian.jira.issue.index.IssueIndexingService

import com.atlassian.jira.event.issue.IssueEventManager

import com.atlassian.jira.event.issue.IssueEvent

import com.atlassian.jira.event.type.EventDispatchOption

import com.atlassian.jira.issue.ModifiedValue

import com.atlassian.jira.issue.util.DefaultIssueChangeHolder

import com.atlassian.jira.issue.link.IssueLinkManager

import com.atlassian.jira.issue.link.IssueLinkTypeManager

import com.atlassian.jira.event.issue.link.IssueLinkCreatedEvent

import com.atlassian.jira.event.issue.link.IssueLinkDeletedEvent

import org.apache.log4j.Level

import org.apache.log4j.Logger

import com.atlassian.jira.issue.link.IssueLinkType

def log = Logger.getLogger('atlassian-jira.log')

log.warn("MOUNA: ")

log.warn("MOUNA COMPONENT NUMBERS : "+ issue.getComponents().size())

List<String> componentList = new ArrayList<String>()

def authenticationContext = ComponentAccessor.jiraAuthenticationContext

if (issue.getComponents().size()==0){

    log.warn("MOUNA CAMELIA COMPONENTS")

    issue.update {

    String text= "Issue does not have any components\n"

    setCustomFieldValue('Execution Summary', text)

    }

}else if(issue.getFixVersions().size()==0){

            log.warn("MOUNA CAMELIA VERSIONS")

            issue.update {

                String text= "Issue does not have any fix versions\n"

                setCustomFieldValue('Execution Summary', text)

                }

    

}

else{

            log.warn("MOUNA CAMELIA ELSE")

        int componentSize=issue.getComponents().size()

        for(ProjectComponent component : issue.getComponents()) {

                componentList.add(component.getName())

        }

        issue.update {

            String text= "The super feature "+issue+" will be split into "+componentSize+

            " features, one for each component:\n"

            for(String component: componentList){

                text = text +"-"+ component+"\n"; 

            }

            setCustomFieldValue('Execution Summary', text)

}

// Issue issue

def issueManager = ComponentAccessor.issueManager

def issueFactory = ComponentAccessor.issueFactory

def subTaskManager = ComponentAccessor.subTaskManager

def issueLinkManager = ComponentAccessor.issueLinkManager

def userManager = ComponentAccessor.userManager

MutableIssue newIssue= ComponentAccessor.issueFactory.issue

newIssue.setProjectObject(issue.getProjectObject())

newIssue.setSummary("MOUNA CAMELIA")

newIssue.issueTypeId= 10070

int issueLinkType= 10070

int sequence =1

newIssue.setAssignee(userManager.getUserByName("mouh"))

newIssue.setDescription(issue.getDescription())

                for(String component: componentList){

                    log.warn("MOUNA CAMELIA component"+ component +" NEW ISSUE "+ newIssue)

                     log.warn("MOUNA CAMELIA Component "+ component+" issue.getId() "+ issue.getId()+" issueLinkType "+issueLinkType+" sequence "+ sequence+" auth "+authenticationContext.getLoggedInUser())                

                    issueLinkManager.createIssueLink(issue.getId(), newIssue.getIssueTypeId(), issueLinkType, sequence, authenticationContext.getLoggedInUser())

        }

}

What about any message in the log files?