Rebilly added an extra criteria option for Rules Match Condition - Unknown and not Unknown.
Unknown means that the selected field value should be null in the Database to match this criteria.
Not Unknown means that the field should be anything but null.
An example Unknown field would be a Bank Country for Payment Card in Transactions. Bank Country can be set to a specific country ID in the Database, or be null (unknown).
For example, when creating a Rule for Gateway Account Requested event, it is possible to create a certain condition that would match the null value.
The screenshot above shows an "IN or Unknown" condition. So, when a Bank Country of Payment Card is not "CA" or it is not set in the Database at all (null), then this Rule would be executed.
To create an Unknown condition, click "Allow unknown (null) value" checkbox in the criteria field options. Then click "Unknown" or "Not Unknown" switch button to specify which condition you want to apply.
It is possible to apply Unknown option to In List criteria as well. So the match condition would be, for example, Bank Country is in List or is Unknown (null).