Checkpoint for relevant variables for different matrix types

[Phuong-Le]

https://github.com/AlexandrovLab/SigProfilerPlotting/blob/db6d54ceb45ac8b6844efadd5175f30ad8333aaa/sigProfilerPlotting/sigProfilerPlotting.py#L6406

SBS4608 is throwing a ZeroDevisionError for me. I can see that you already have a checkpoint for mutation_count_total https://github.com/AlexandrovLab/SigProfilerPlotting/blob/db6d54ceb45ac8b6844efadd5175f30ad8333aaa/sigProfilerPlotting/sigProfilerPlotting.py#L6288, so the error was potentially because ratio_total is 0? I'm wondering if you could add some checkpoints for the relevant variables as well?