Fix log scale visualization if a 0 is present in the output
This issue is reproduced with the default "sample data", trying to visualize for example Pyrrothite in log scale. 0 is a possible value for Pyrrothite, and in this case the y-axis is not correctly computed, I guess since the logarithm of 0 is -infinity AND 0 is the minimum of the variable.
If log is wanted, restrict y-axis computation to minimum value > 0.