The user does not realize when this exception happens that it happens because no fragilities match the buildings. The exception is thrown because initially we were adding fields to the building dataset to hold the damage analysis, but if no fragilities are found, nothing was being entered into the columns and geotools did not like this. When we called CollectionDataStore to get the FeatureSource, it said it couldn't find it (probably because of a field mismatch, or the lack of data in the fields).