SOSI: fix memory leaks and use of uninitialized memory

git-svn-id: https://svn.osgeo.org/gdal/trunk/gdal@25955 f0d54148-0727-0410-94bb-9a71ac55c965
SOSI: fix errors and segfault found by running test_ogrsf

git-svn-id: https://svn.osgeo.org/gdal/trunk/gdal@25956 f0d54148-0727-0410-94bb-9a71ac55c965