#2855 metadata tab, statistics, min and max don't skip fill

[Jeremy Faden]

I just noticed the min and max on the statistics node of the metadata tab don't skip fill, or at least "fill" is reported for both when there is valid data.

file:///project/rbsp/data/density/mature/rbsp-a/rbsp-a_$x_orbit-$x_density_y_aut$x.dat?column=quality

[Jeremy Faden]

The min and max reported are the extent of the non-zero bins of the histogram.