Fix freeing non-heap memory
Fix freeing non-heap memory

In the exceptional case when the function oscap_textlist_get_preferred_plaintext returns NULL, we'd try to free a non-heap memory.

Signed-off-by: Wesley Ceraso Prudencio <b02f0a9e9fb75238061eadf104399137f90ddb2e@redhat.com>

mpreisler/openscap,jan-cerny/openscap,OpenSCAP/openscap,redhatrises/openscap,OpenSCAP/openscap,jan-cerny/openscap,mpreisler/openscap,jan-cerny/openscap,OpenSCAP/openscap,mpreisler/openscap,mpreisler/openscap,jan-cerny/openscap,mpreisler/openscap,redhatrises/openscap,OpenSCAP/openscap,redhatrises/openscap,OpenSCAP/openscap,mpreisler/openscap,OpenSCAP/openscap,redhatrises/openscap,redhatrises/openscap,jan-cerny/openscap,redhatrises/openscap,jan-cerny/openscap