Output file names for LossDataSink can't have prefixed dots if no extension is provided
Instead of correct paths an empty string is returned in
ElementBase::getOutputFN()if the paths start with a prefixed dot such as e.g.
../ and the file name doesn't include an extension. The user shouldn't have to use a file name with extension, the extension is provided by Opal anyway to support both ascii and HDF5 output.