message: Group::Iter_visit: replace unwraps with expects
diff: @@ -319,10 +319,10 @@ impl Group {
  {
  panic::catch_unwind(|| {
  let vtable = op_data.cast::<Vtable<F, G>>();
  - let vtable = unsafe { vtable.as_mut().expect("op_data is always non-null") };
  + let vtable = unsafe { vtable.as_mut().expect("iter_visit: null op_data ptr") };
  let name = unsafe { std::ffi::CStr::from_ptr(name) };
  - let info = unsafe { info.as_ref().unwrap() };
  - let handle = Handle::try_new(id).unwrap();
  + 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");
  handle.incref();
  let group = Group::from_handle(handle);
  if (vtable.f)(&group, name.to_string_lossy().as_ref(), info.into(), vtable.d) {
  