If you create a custom editor in the EditorNeeded event or method override, and don't set the editor's value, an exception is thrown. Reproducible only with DataProvider. To work this around set the custom editor's initial value to a value different than null. Or you can use the events instead of DataProvider.
UPDATE: The issue occurs in both cases - when populating with data manually and through DataProvider. We will be able to provide a fix for the DataProvider case, as well as the manual popupating if you use TextBox for editor. If populating manually and you need to use a different editor such as DateTimePicker for example, you will need to handle its background on creation.
Available in LIB version 2017.3.1113, it will be also available in the R1 2018 Release.