I am getting the below error in Salesforce which is prohibiting me to enter or edit any contacts.

Error: Invalid Data.
Review all error messages below to correct your data.
Apex trigger CnP.householdadd caused an unexpected exception, contact your administrator: CnP.householdadd: execution of BeforeInsert caused by: System.ListException: List index out of bounds: 0: (CnP)