Default of an attribute definition gets blanked out, when the value set against it is made inactive.
Steps to reproduce:
1. Create a static lookup with three values within it
2. Use this lookup to create a custom attribute in the 'Investment' object, of data type 'Lookup'. Select a value to be the default
3. Now, go back to the lookup from step 1. Deactivate the value set in step 2
Actual Result: The value is not longer visible in the attribute definition
Expected Result: The value is still visible in the attribute definition.
Release : 16.1.3
DE77571 is under review.