S57: robustness fix against missing XCOO or YCOO subfields

git-svn-id: https://svn.osgeo.org/gdal/trunk/gdal@25827 f0d54148-0727-0410-94bb-9a71ac55c965
S57: robustness fix against missing XCOO or YCOO subfields

git-svn-id: https://svn.osgeo.org/gdal/trunk/gdal@25828 f0d54148-0727-0410-94bb-9a71ac55c965