Prevent Deselection Focus

PreventDeselectionFocus.cs

using UnityEngine;
using UnityEngine.EventSystems;

public class PreventDeselectionGroup : MonoBehaviour
{
  private EventSystem evt;
  private GameObject sel;

  private void Start()
  {
    evt = EventSystem.current;
  }

  private void Update()
  {
    if (evt.currentSelectedGameObject != null && evt.currentSelectedGameObject != sel)
      sel = evt.currentSelectedGameObject;
    else if (sel != null && evt.currentSelectedGameObject == null)
      evt.SetSelectedGameObject(sel);
  }
}