Fix for dummy blocks not working

Dependent of the version of SimpleXML, on some systems the names of the `<dummy_blocks>` were put in the keys instead of the values of `$esiOptions['dummy_blocks']`.
This caused them not to work.
My solution may fix #473 and #178. Of cause you still need to use the `<dummy_blocks>` in the right way, but previously the dummy blocks may not have worked on particular systems