I'm trying to create a trigger on Asset, after Undelete.

I simply want to set a flag to denote that the record has been undeleted.

 I expect that I should be able to do something like the following, but I get an "Attempt to de-reference a null object" error on the for loop line.

{

    for(Asset undeletedAsset : trigger.old)

  {

     Asset theAsset = [select undeleted__c from Asset where id in :trigger.old];

     theAsset.undeleted__c = true;

     update theAsset;

  } 

}

Any help or pointers are greatly appreciated.

Thanks

Jon