message: Group::Iter_visit: also check for null name ptr
diff: @@ -320,6 +320,7 @@ impl Group {
  panic::catch_unwind(|| {
  let vtable = op_data.cast::<Vtable<F, G>>();
  let vtable = unsafe { vtable.as_mut().expect("iter_visit: null op_data ptr") };
  + unsafe { name.as_ref().expect("iter_visit: null name ptr") };
  let name = unsafe { std::ffi::CStr::from_ptr(name) };
  let info = unsafe { info.as_ref().expect("iter_vist: null info ptr") };
  let handle = Handle::try_new(id).expect("iter_visit: unable to create a handle");
  