[Dropdown] False positive `isSelected` when descendant cannot be found

[JaceHensley]

🐛 Bug report

Current Behavior

isSelected is set based on comparing index and selectionIndex. But if the descendant cannot be found and there is no selection the menu item is incorrectly marked as selected

let isSelected = index === selectionIndex && !disabled;

On the next render this is fixed because the descendant can be found.

Expected behavior

On first render if a descendant cannot be found do not mark it as selected

Suggested solution(s)

Adding an additional check that the index is greater or equal to 0

let isSelected = index >= 0 && index === selectionIndex && !disabled;

Additional context

I'm actually using menu-button in custom components. A not rendering the MenuPopover until isExpanded is true, cause I'm on React 18 and following the suggestions here

Your environment

Software	Name(s)	Version
Reach Package	menu-button	0.18.0
React		18.2.0
Browser	Firefox	113
Assistive tech	-	-
Node		16
npm/yarn	yarn	1.22.19
Operating System	macOS	13.3