Avoid overwriting output type in onnx graph (#25906)
Summary:
When creating the onnx graph, we overwrite the output type with the output type of the PT graph.
In some special cases, when using scripting, the PT graph does not have type information. We want to avoid overwriting the input type is these cases.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/25906
Reviewed By: hl475
Differential Revision: D18645903
Pulled By: houseroad
fbshipit-source-id: 56acc43e0c15c74ac8ebd689e04f7371054e362e
