Fix small memleak (trunk only)

git-svn-id: https://svn.osgeo.org/gdal/trunk/gdal@28089 f0d54148-0727-0410-94bb-9a71ac55c965
GPKG: implement metadata reading and writing

git-svn-id: https://svn.osgeo.org/gdal/trunk/gdal@28090 f0d54148-0727-0410-94bb-9a71ac55c965