Give a relevant error message if administration.xml is corrupted or empty

We've recently had an issue where we ran out of disk space on our bamboo server. This caused the administration.xml (in (bamboo-home/xml-data/configuration) to be empty when we tried to restart Bamboo. The logs did not give any helpful error message and I only found this KB-article after I googled each of the nested exceptions.

It would help greatly if Bamboo would tell you there's a problem with one of the config-files and not just give you a BeanCreationException.