[ONNX import] Gemm operator impossible to infer

Problem description

After importing an ONNX model containing the [Gemm] operator, it is impossible to infer the model.

The error message "Undefined mandatory input #2 (closed) for node [Gemm__39 - (Gemm)]" is displayed, and the calculation crashes (core dump).

Reproducible example code

Here are the files to reproduce the issue: usecase.tar.gz

Just run: python export_model.py