CRM_Contribute_BAO_Query::whereClauseSingle() does not handle unknown fields nicely

We changed the name and types of a few checkboxes in 4.2 (thankyou_text, receipt_sent) to radio boxes in 4.3. As such the code no longer recognizes these field names which are present in smart searches

We have a few options for this:

1. Handle these fields in a nice manner and emit a warning. This prevents the error and lets the user know that something is amiss and should be fixed

2. Fix these searches when we upgrade and change the field names there. These are serialized values spread across a table or two

3. Add backward compatibility code within the query builder. I dont like this option