Supervisory Node does not update after removing the unrequired fields

While checking OLMIS-5625, I noticed that when I delete data from fields that are not required, the changes are not saved.

Reproduction steps:

1. Log in as an administrator;

2. Go to Administration > Supervisory Nodes;

3. Click the Edit button next to any Supervisory Node;

4. Delete "Associated Facility", "Parent Node", remove Child Node and click "Update Supervisory Node button;

5. Return to editing the previously selected Supervisory Node.

Result:
The changes have not been saved.

Expected result:
After clicking "Update Supervisory Node" button the changes should be saved.