Fix a bug of C++ L-BFGS optimizer (#27606)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/27605: The C++ L-BFGS Optimizer will not work properly if there are one or more registered tensors with no grad in the model:
```
terminate called after throwing an instance of 'c10::Error'
what(): There were no tensor arguments to this function (e.g., you passed an empty list of Tensors), but no fallback function is registered for schema aten::view. This usually means that this function requires a non-empty list of Tensors. Available functions are [CUDATensorId, QuantizedCPUTensorId, VariableTensorId, CPUTensorId, MkldnnCPUTensorId] (lookup_ at /pytorch/aten/src/ATen/core/dispatch/DispatchTable.h:245)
```
Add some `if (!parameter.grad().defined()) {...}` in the ` torch/csrc/api/src/optim/lbfgs.cpp`
Pull Request resolved: https://github.com/pytorch/pytorch/pull/27606
Differential Revision: D17866550
Pulled By: yf225
fbshipit-source-id: bcaf0bf75b93c57304856b03d8984c1617ebbfef
