elda:missingEndpoint instead of 404 on item endpoints that use api:selector

[skwlilac]

Ususally elda ItemEndpoints are set to use api:itemTemplate based URI patterns, However, there are unusual cases where an api:selector is used to specifiy a selector intended to return a single value.

However, if the selector fails to return any items, elda 'invents' the URI elda:missingEndpoint as a primary topic for the otherwise empty page.

If api:itemTemplate is used elda either 404s or may return an empty response page depending on the setting of _exceptionIfEmpty.

Please could you alter the behaviour of selector based item endpoints to mirror the behaviour of item template based item end points or at least make such behaviour a configuration option,

Example:
http://landregistry.data.gov.uk/data/hpi/region/shropshire/month/2017-02

compare with

http://landregistry.data.gov.uk/data/hpi/region/shropshire/month/2016-02