[BUG] After a UI item is deselected from a mouse, select the default UI

[japtar10101]

Describe the bug

If one clicks outside of the menu, none of the buttons will be selected. This is not good if the player is about switch from keyboard or controller. If no UI is selected for a fraction of a second, automatically select the default button for that menu.

To Reproduce

Steps to reproduce the behavior:

1. Run the Main Menu scene.
2. Plugin the controller. Confirm the start menu can be navigated.
3. Use the mouse to hover away from the current UI element.
4. Attempt to navigate the menu again.

Expected behavior

Controller navigation still responds.

Actual behavior

Controller navigation does not respond. No UI element is highlighted, so navigation is not possible.

Additional context

Carry-over from the old Bitbucket Mercurial project:
https://bitbucket.org/OmiyaGames/hg-template-unity-project/issues/39/after-a-ui-item-is-deselected-from-a-mouse

[japtar10101]

In theory, this is fixed, but needs verification.