Return list of one default option when shape not enabled (2/2)

This is to return a list of one default option (circle) if the shape
cutstomization flag is not turned on.

It resolves the issue that the selected shape option never emits.

Test: Manually tested
Fixes: 388299893
Flag: com.android.systemui.shared.new_customization_picker_ui
Change-Id: I400717a300eca49d8e03904d83c51311493e3eea