NullPointerException when a raw data type is missing

[Nicklas Nordborg]

If a raw data type is removed from the raw-data-types.xml file and there are raw bioassays in the database that uses the removed raw data type, the call to RawBioassay.getRawDataType() will return null. This causes a lot of trouble for many parts of the code since null is not an allowed return value. I think the Experiment.getRawDataType() may be affected by the same problem.

Since the configuration is in an external file there are no database constraints that we can lean on to make sure that used raw data types are never deleted. Maybe we can have a "dummy" raw data type so we don't have to return null.