Blank permissible values for enumerations

[martinwellman]

We have enumerations where a blank value (ie. "") is a valid enumeration value. It usually corresponds to "Not Applicable" or something similar. The slot, however, might still be a required slot. With Schemasheets having a blank value in the permissible_value column will make that row correspond to the top-level enum, rather than an enum value. So the description and title (and maybe other fields) on such rows would be assigned to the top-level enum, rather than creating a new permissible_value that is blank. Is there a way to specify blank permissible values with Schemasheets?