D13794 changed ArcanistPHPCloseTagXHPASTLinterRule to ignore inline HTML blocks, but selectDescendantsOfType returns an AASTNodeList (which always exists).
Instead, check that the count() of the node list is > 0.
empty.lint-test had to be changed, it wouldn't have been accepted had this rule not been broken before it was commited.
Added tests to cover ArcanistPHPCloseTagXHPASTLinterRule in the future.