Entities' System window allows for all data Columns to be disabled

Steps to reproduce:

1. Open the attached project
2. Open the SampleScene
3. In the Systems window, right-click on one of the column names
4. Observe the contextual menu, which allows toggling the visibility of the columns
5. Attempt to disable all data columns

Actual results: User is allowed to disable all data columns, leaving an empty list

Expected results: The Systems window ensures that at least one column is visible

Reproducible with versions: 6000.5.0a2, 6000.5.0a9, 6000.6.0a1

Not reproducible with versions: 2022.3.74f1, 6000.071f1, 6000.4.0f1, 6000.5.0a1 (Ability to disable/enable the visibility of data columns was not present)

Tested on (OS): macOS 26.3.1

Notes:

• This safeguard exists in the Entities' Search Node Hierarchy window, where disabling any last active data column is prevented
• A similar safeguard exists in the Hierarchy V2, where the Name column cannot be disabled