Default value cannot be removed using Metadata manager

[Fernananas]

How to Reproduce

There is a default value used in any datatype.
Go to the metadata manager, remove default value and save all changes.
Then an error occurs, two examples:
example one is categorical:

example two is mref:

Expected behavior

When using metadata manager to remove default value, saving would be possible without error.

Observed behavior

Default value cannot be removed by using metadata menager