scale arg is recycled if it has unit length and length(potential) > 1. This saves the user some typing and makes the functions as.SHE() and from.SHE() easier to use.
The matching algorithm would fail for any electrode scale that had string in potentials.as.SHE()$conc.string that was not "saturated" (which happened to be the alkali metals). Fixed this issue by making the matching step-wise, and adding a few more checks for zero rows returned.
Previous behaviour returned NAs for values that were already vs SHE. That issue now fixed. The fix included added SHE (zero at all temperatures) to as.SHE.data.