Optimizer reports "Unresolved value references" since v0.3.0

[zhenhuaw-me]

Via pipeline https://github.com/zhenhuaw-me/onnxcli/actions/runs/3453474851/jobs/5764096907.

A simple model works no issue till optimizer v0.2.7 (verified locally), but starts to fail with optimizer v0.3.0 (verified locally) and still fail with v0.3.2 (the pipeline).

It's onnx optimize ./assets/tests/conv.float32.onnx optimized.onnx.