f90nml: Zero-indexed array indices are ignored

If we have a zero-indexed array, e.g.

&nml_group
    y(0:3) = 1, 2, 3, 4
/

then it incorrectly interprets 0 as None (due to a bug in FIndex) and uses the default value of 1. The above case fails because there are more than 3 values in the array and the iterator runs out of indices.