UocFilterBuilder can't be set to a null/empty value
It seems impossible to have a UocFilterBuilder on a page that defaults to a null value (or can be changed back to a null value) - a default "all objects" filter is always present.
This can be a problem, for example when creating a custom object with both Explicit Membership, and a Filter for criteria membership
It may be that only the manually managed membership is required, in which case the Filter should be null, and the value of ComputedMember should be equal to ExplicitMember.
However, if the RCDC contains a UocFilterBuilder, it will always default to something, e.g. /User, and add all objects of that type to ComputedMember along with the ExplicitMembers specified.
Workarounds include putting the filter builder on a separate tab to try and prevent it being viewed (in which case it doesn't modify the Filter attribute on editing the object), but anyone who views the tab and has permissions (even if it is just admins) may still accidentally add a filter to an object that shouldn't have one.
Another workaround may be to default the Filter to something that will return no objects, but that seems like a bodge.
It would be better if there was just a way for the filter builder to start off empty, rather than default to adding all objects.