Properly handle 404's from get_policy_search endpoint

[anth-volk]

In conjunction with RESTful expectations, PolicyEngine/policyengine-api#1854 returns a 404 when no records are found from the get_policy_search endpoint. However, that's not necessarily an indication of failure, just that no records have been found. We'll need to update the policy search box to allow 404's and just to output no policies, instead of erroring, which I believe is only console logged at the moment in prod, but throws a runtime error while testing.