fixed 2 crashes when accessing an (ill-formed?) CityGML file via the GML dirver

GDAL ticket: http://trac.osgeo.org/gdal/ticket/4975
Revert "fixed 2 crashes when accessing an (ill-formed?) CityGML file via the GML dirver"

This reverts commit cf4497b0eae848526801409e9487b49d38a073a0.