[ExecuTorch] Cannot Convert Empty Model

[YifanShenSZ]

This toy model fails in ExecuTorch

        class IndexModel(torch.nn.Module):
            def forward(self, x):
                if len(shape) == 2:
                    return x[:, :]
                elif len(shape) == 4:
                    return x[:]

It contains only a no op, so ExecuTorch would simply return its input

However, in Core ML input and output must have different names