If a domain has no snapshots and 'virsh snapshot-list' is called,
this gets all the way down to virshSnapshotListCollect() which
then collects all snapshots (none), and passes them to qsort()
which doesn't like being called with NULL:
extern void qsort (void *__base, size_t __nmemb, size_t __size,
__compar_fn_t __compar) __nonnull ((1, 4));
Resolves: https://gitlab.com/libvirt/libvirt/-/issues/533
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>