Getting "Cannot invoke method getCreated() on null object” : created scripted field for Last comment

[Nilanjana Misra]

I have created a scripted field to capture the last comment in a story- Last Comment

import com.atlassian.jira.ComponentManager
import com.atlassian.jira.issue.Issue
import com.atlassian.jira.issue.comments.Comment
import com.atlassian.jira.issue.comments.CommentManager
import com.atlassian.jira.component.ComponentAccessor

def commentManager = ComponentAccessor.getCommentManager()
def comment = commentManager.getLastComment (issue)
def date = comment.getCreated()
if(comment!=null)

{ return ((date as String) + " " + comment.body + " Author: " + comment.authorFullName) }

return "null";

I am getting below error
2018-02-07 01:05:35,694 ERROR [customfield.GroovyCustomField]: *************************************************************************************
Script field failed on issue: SPD-****, field: Last Comment
java.lang.NullPointerException: Cannot invoke method getCreated() on null object
at Script140613.run(Script140613.groovy:9)

I am not a engineer ,so please help me with the code.How do i fix this NPE.
BTW the template I have used in Text field Multiline and Free Text Searcher
Please help !!

[Kyle Moseley · Accepted solution]

The error is telling you that it cannot use the method getCreated() against a blank comment. A quick fix would be to put the offending line (date variable declaration) within the THEN portion of the IF statement. Then, it will not attempt to perform this method against a null object because you are already testing for it.