Catch ValueError when parsing XML documents

Ignore-this: 372dac1df00055c21f8f9d3e5e91a03f

darcs-hash:20130618134027-56b4d-183b64d4b30903058636fa40754f3460ddd4d591
Publish instance id over Bonjour

Ignore-this: d7455e674c297b595087feb09ffe6b66

darcs-hash:20130618135355-56b4d-c5d653bf7917ddf08f579ce64f3844f09349f9a7