Added explicit Qnil return for dense storage iterators.  Fixes #51.
Added explicit Qnil return for dense storage iterators.  Fixes #51.

agisga/nmatrix,thisMagpie/nmatrix,agisga/nmatrix,johnmarinelli/nmatrix,thisMagpie/nmatrix,agisga/nmatrix,janusnic/nmatrix,wlevine/nmatrix,janusnic/nmatrix,janusnic/nmatrix,wlevine/nmatrix,thisMagpie/nmatrix,thisMagpie/nmatrix,johnmarinelli/nmatrix,agisga/nmatrix,janusnic/nmatrix,wlevine/nmatrix,johnmarinelli/nmatrix,johnmarinelli/nmatrix,wlevine/nmatrix