The page http://wiki.mt-daapd.org/wiki/XML_Client_API describes the XML API, and at the bottom lists a number of extensions specific to the Firefly (née mt-daapd) server. Some of these, at least, appear to be broken in r1450 and r1465. Are these extensions not supported in the Firefly incarnation of mt-daapd? In any case, I doubt that the correct behavior is a crash.
Bug from the migration of daap to a module, I think. I’ll take a closer look at it.