There is a Bug in ant 1.8.3 and 1.8.4 that produces a NPE when a filter should be applied to an empty file: https://issues.apache.org/bugzilla/show_bug.cgi?id=53626
As ant 1.8.4 ships with some versions of OS X and a workaround is really simple it would be good to avoid empty files in DSpace. Currently there are two empty files in the configuration of the RDF export. Adding two empty lines into these files resolves the problem. The empty files exists, so that users see the possiblity to add RDF statements into them while the default configuration doesn't.