Resolving an EntityReference of type Page to Document doesn't check page existence

Resolving an EntityReference of type Page such as wiki:Space/Page to a Document EntityReference should return wiki:Space.Page if that page exists. Right now the resolver always return wiki:Space.Page.WebHome without performing any check.

This bug is very visible when resolving a PageResourceReference to a Document type, since the DocumentResourceReferenceResolver does perform this kind of check so there's an inconsistency here.