Check for Primary Sales Rep - Simple script error question

I'm deploying a script that will stop a user from saving a new opportunity without a primary sales rep identified. It seems simple enough but I am getting an error I'm not familiar with.

Script/Deployment Details:
Type: Client
Name: cs_SalesRepCheck
Save Record Function: clientSaveRecord
Deployed: True
Status: Testing
Event Type: Create

Script Code:

function clientSaveRecord(){      var salesrep = nlapiGetFieldValue(salesrep);      if (!(salesrep)){          alert("No Primary Sales Rep Identified. Please choose a primary sales rep before saving.");          return false;      } else {          return true;      }  }

The error being returned on save is:

An unexpected error occurred in a script running on this page.