“NullReferenceException” error is thrown and the Entities Systems columns break when reordering the columns

Steps to reproduce:

1. Create a new Unity project using the Universal 3D template
2. Install the Entities package (com.unity.entities)
3. Create a new Sub Scene in the Hierarchy window
4. Open the Entities Systems window (Window > Entities > Systems)
5. Click and drag the "System" column to the right of the "World" column
6. Observe the Console window

Actual results: The column visual breaks and a “NullReferenceException” error is thrown

Expected results: No errors are thrown

Reproducible with versions: 6000.5.0b9, 6000.6.0a5

Can’t test with versions: 6000.0.0f1, 6000.0.75f1, 6000.3.16f1, 6000.4.8f1 (cannot reorder the columns)

Tested on (OS): MacOS Silicon Tahoe 26.3