Fix error handling in PKF smoother

Problems in solving will crash Dynare: extract_smoothed.mod data_final2.xlsx

added bug occbin labels

@JohannesPfeifer: beyond fixing error handling, I am working to prepare a PR that would also let the smoother run properly also in this case.

made the issue confidential

made the issue visible to everyone

The .mod and .xlsx files have been deleted due to intellectual property issues.

mentioned in merge request !2123 (merged)

solved in !2123 (merged)

closed