AttributeErrors in SHA256 class functions when seed=None

[ackaplan11]

When you create a new SHA256 object using the constructor without parameters
sha256 = SHA256(),

the following functions will return AttributeErrors
sha256.jumpahead() --> AttributeError: 'NoneType' object has no attribute 'update'
sha256.next() --> 'AttributeError: NoneType' object has no attribute 'update'
sha256.random() --> AttributeError: 'NoneType' object has no attribute 'digest'
sha256.randint_trunc() --> AttributeError: 'NoneType' object has no attribute 'digest' -- (Depricated)
sha256.getrandbits() --> AttributeError: 'NoneType' object has no attribute 'digest'
sha256.randbelow_from_randbits() --> AttributeError: 'NoneType' object has no attribute 'digest'
sha256.randint() --> AttributeError: 'NoneType' object has no attribute 'digest'