Fix handling none source in build_torch_function_fn (#119724)
Fix https://github.com/pytorch/pytorch/issues/119580
When a UserDefinedObjectVariable is created it does not always have a source, i.e: when its an intermediate
This diff fix two handling of none source in two locations during an inlining of a user torch function.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/119724
Approved by: https://github.com/jansel, https://github.com/mlazos, https://github.com/anijain2305
