Bug Error With Behaviour Plugin

[Kumar]

Hi Team,

I have tried One task with Behaviour Plugin I added a script

def reporter = underlyingIssue.reporter?.displayName

 if(reporter.equalsIgnoreCase("kumar")){
 getFieldById("description").setReadOnly(true) 
}else{
 getFieldById("description").setReadOnly(false)
}

This script is for Kumar created tickets other user cannot edit the desctiption for Kumar created tickets

The only  Problem is when i try to edit other user created issue a screen is popping i'm wondering that what is the reason

can any one suggest me please

Thanks,

Kumar