I have a trigger that fires off when a field called "FIMS_FundID__c" is updated.  code looks like this:


trigger Z_TDF_TaskOnUpdate on Task (after update) {
    if(trigger.isUpdate){
        for(Task t : Trigger.new){
            Task oldTask = Trigger.oldMap.get(t.Id);
            if ( t.FIMS_FundID__c != oldTask.FIMS_FundID__C)
            {
              String userEmail = 'bgordon@dallasfoundation.org';
              Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage(); 
              String[] tmp = new String[]{'bgordon@dallasfoundation.org'} ;
              mail.setToAddresses(tmp); 
              mail.setInReplyTo('noreply@dallasfoundation.org');
              mail.setSenderDisplayName('Salesforce CRM Notification');
              mail.setSubject('ID CHANGED for record ' + t.FIMS_ID__c ); 
              String body = 'The Fund ID changed on activity record # ' + t.FIMS_ID__c + ' from ' + oldTask.FIMS_ID__c + ' to ' + t.FIMS_ID__c + '.'; 
              mail.setPlainTextBody(body); 
              Messaging.sendEmail(new Messaging.SingleEMailMessage[]{mail});
            }
        }
    }    
}


When the field is updated, the email is sent, but the values are "null"

So the subject reads: ID CHANGED for record null
and the body of the email reads:  The Fund ID changed on activity record # null from null to null.

does anyone know why the null values appear?  If I use "t.Id" or oldTask.Id, they show up in the email correctly, but none of the other fields do.