Sorry I just noticed there is an inconsistency between the JDBC Request step and the REST request, so right now it should be responseAsXML.
Anyway, is your JDBC request step called "jdbc_properties"? The XML exception usually means that there is no content to work on, so I suspect you are not actually getting the result.
Start using log statements to get the response, like this:
log.info context.expand( '${stepname#ResponseAsXML}')
where stepname is the name of your JDBC Request step.
If you see the response, then work on getting the xpath right, otherwise something else is wrong.
You could also attach the project so someone can take a look.
