When you create a new dataset with the dataset editor, the dataset description and class descriptions are set to an empty string: ""

When a dataset is created by uploading a csv file, if there is no description for a class, the description value is set to null.

We should make the following changes:

• Set the description to '' when uploading by csv
• If possible, use the same submission logic for both of these processes if not already done, so that we have the same behaviour
• Alter the schema to make the description field of a dataset and a dataset_class to not null
• Change any datasets with null values