Bibliotheca bibliographic response for title no longer in collection not handled properly

[leonardr]

When a title leaves the collection, Bibliotheca starts sending this in response to your request for bibliographic information:

<ArrayOfItem xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" />

(It might be when the book leaves Bibliotheca, but the problem is the same.)

BibliothecaBibliographicCoverageProvider treats this as a transient error communicating with Bibliotheca. It should treat this as a successful attemp to commnunicate with Bibliotheca which reveals nothing new about the bibliographic information.