Problem LINQ

Hi all,

I'm having a problem in a Plugin and it's related to a LINQ query that I'm trying to do, the code throwing the error is the next:

//'List' object is an Array of records of a Custom Entity, in this case it has 675 Record Objects and only 1 is Active

//In the line below I'm trying to retrieve all Account Id's from the records contained in 'List'. I was debugging the code and all objects has pwc_AccountId.Id as a property

  var test = List.Select(bp => bp.pwc_AccountId.Id).ToList();

The error that I'm getting is:

Object reference not set to an instance of an object

I don't really understand why I'm getting this error, as long as I can see there's no Null or empty object in that line code.

Do you guys know what could be the problem here?

Thanks in advance!