do not check pointers after dereferencing them

Two instances, both spotted by Coverity.  In one, two blocks were
swapped.  In the other, the check is not needed anymore.

Cc: qemu-stable@nongnu.org
Cc: qemu-trivial@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
