Hydrogens in mol blocks have a valence value set

[greglandrum]

Reported by James Davidson and Roger Sayle

In [1]: from rdkit import Chem

In [2]: m= Chem.AddHs(Chem.MolFromSmiles('C'))

In [3]: print Chem.MolToMolBlock(m)

     RDKit          

  5  4  0  0  0  0  0  0  0  0999 V2000
    0.0000    0.0000    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
    0.0000    0.0000    0.0000 H   0  0  0  0  0  1  0  0  0  0  0  0
    0.0000    0.0000    0.0000 H   0  0  0  0  0  1  0  0  0  0  0  0
    0.0000    0.0000    0.0000 H   0  0  0  0  0  1  0  0  0  0  0  0
    0.0000    0.0000    0.0000 H   0  0  0  0  0  1  0  0  0  0  0  0
  1  2  1  0
  1  3  1  0
  1  4  1  0
  1  5  1  0
M  END

The valence on the H is clear, it shouldn't be set in the mol block.