We create a 'lease_new' when we are adding new lease entry, then later
in the code we add the 'lease_new' into a 'leases_array_new' which
leads into the crash because we double free the 'lease_new'.

To prevent the double free we set the 'lease_new' to NULL after
successful append into the 'leases_array_new'.
Signed-off-by: NPavel Hrdina <phrdina@redhat.com>