Summary:
instead of `errors: ?Array<Error>` and setting it back to `null` to clear errors, which Flow is not very happy with, we can make it always an array and truncate it with `errors.length = 0`.
Changelog: [Internal]
Reviewed By: motiz88
Differential Revision: D33584184
fbshipit-source-id: 81b424e69e60203c645bafbac12177ffcdc0c6ef