Getting Null pointer error while fetching catalogitem informations

Hi Team,
I am using one desktop and trying to fetch the catalogitems along with the associated attributes from one metadata reader. However i am getting an null pointer error, would really appreciate if there are any fix or solutions around the same
“Internal error occurred during run of the plan: Cannot invoke "com.ataccama.one.client.impl.MdAncestor.getProperty()" because "this.ancestors[i]" is null”