When creating popover with `UI_popover_begin` the popover block
is created just once without a region and since `UI_popover_begin` blocks
are not support refreshing, layout panels may not be compatible
in this kind of popover since open/close state cannot be refreshed either.
Only `UILayout.popover(...)` popovers are supported to have layout panels.
Pull Request: https://projects.blender.org/blender/blender/pulls/119796
7fabf0d896