Required properties nested inside optional properties still required in strict mode

[thewilkybarkid]

We run in strict mode, but it seems that properties are still required even if their optional parent isn't:

With Property hydra:member {
  Expect Type schema:Article
  Expect Property schema:name
}

fails if hydra:member is not present (Strict mode requires that all steps are executed), but they should only be tested if it is there. (Skipping missing property http://www.w3.org/ns/hydra/core#member happens correctly.)

(Refs https://httpapis.slack.com/archives/C1JP575EX/p1579613791005300).

[tpluscode]

Deployed as docker image hydrofoil/hypertest:_0.4.1