Segmentation violation when using --useLogVal
In case negative values are inside the cell current list (which normally should not happen), the plotting with --useLogVal crashes with a segmentation violation.
An example with the latest develop branch that crashes is this one: ./bin/HexPlot --colorpalette 57 -g ./geo/hex_positions_HPK_256ch_8inch.txt -o CERN_3007_IV.pdf -i HGCAL_test_results/Results/HPK_8in_271ch_3007/HPK_8in_271ch_3007_IV.txt --select -600 -z -0.01:10000 --invertVal --useLogVal
At -600V, the cell list has at least one positive value, which is converted to negative values when using --invertVal.