Summary:
`getChilAt` can return `null` (see also line 671), probably when the UI changes during the inspection process. Added a null check that should protect against the failure reported in P501013941
Changelog: Fixed NPE during search in layout plugin (Android)
Reviewed By: lblasa
Differential Revision: D36369508
fbshipit-source-id: 1f066d1a73bdfe875d66f7200ded0d0776af8321