[BUGFIX] Fix Warning if configuration wizard is empty

It may happen configuration wizard is empty. In this case, method
xml2array will return a debug string telling something went wrong. Since,
later in the code, it is assumed the output of xml2array is an array, a PHP
warning will be raised on the FE.
Merge pull request #135 from fudriot/master

[BUGFIX] Fix Warning if configuration wizard is empty