HANConv: NaN handling (#4841)

* update

* changelog

CHANGELOG.md

@@ -12,7 +12,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Added Python version requirement ([#4825](https://github.com/pyg-team/pytorch_geometric/pull/4825))
 - Added TorchScript support to `JumpingKnowledge` module ([#4805](https://github.com/pyg-team/pytorch_geometric/pull/4805))
 - Added a `max_sample` argument to `AddMetaPaths` in order to tackle very dense metapath edges ([#4750](https://github.com/pyg-team/pytorch_geometric/pull/4750))
-- Test `HANConv` with empty tensors ([#4756](https://github.com/pyg-team/pytorch_geometric/pull/4756))
+- Test `HANConv` with empty tensors ([#4756](https://github.com/pyg-team/pytorch_geometric/pull/4756), [#4841](https://github.com/pyg-team/pytorch_geometric/pull/4841))
 - Added the `bias` vector to the `GCN` model definition in the "Create Message Passing Networks" tutorial ([#4755](https://github.com/pyg-team/pytorch_geometric/pull/4755))
 - Added `transforms.RootedSubgraph` interface with two implementations: `RootedEgoNets` and `RootedRWSubgraph` ([#3926](https://github.com/pyg-team/pytorch_geometric/pull/3926))
 - Added `ptr` vectors for `follow_batch` attributes within `Batch.from_data_list` ([#4723](https://github.com/pyg-team/pytorch_geometric/pull/4723))

torch_geometric/nn/conv/han_conv.py

@@ -18,6 +18,8 @@ def group(xs: List[Tensor], q: nn.Parameter,
     else:
         num_edge_types = len(xs)
         out = torch.stack(xs)
+        if out.numel() == 0:
+            return out.view(0, out.size(-1))
         attn_score = (q * torch.tanh(k_lin(out)).mean(1)).sum(-1)
         attn = F.softmax(attn_score, dim=0)
         out = torch.sum(attn.view(num_edge_types, 1, -1) * out, dim=0)