Objects going through the dealloc visitor can be only partially allocated.
Detect the situation and avoid a segfault. This also helps with the
input visitor, when there are errors.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>