Include "empty.xml" in build.properties

transformations/org.universaal.tools.owl2uml/build.properties

@@ -12,7 +12,8 @@ bin.includes = plugin.xml,\
                lib/pellet-jena.jar,\
                icons/,\
                profiles/,\
-               lib/concurrent.jar
+               lib/concurrent.jar,\
+               samples/empty.xml
 jars.compile.order = .,\
                      lib/
 src.includes = contexts.xml