CScript.witness_version() should call CSriptOp.decode_op_n() on the value before returning

[dgpv]

python-bitcoinlib/bitcoin/core/script.py

Lines 692 to 694 in 173a73e

	def witness_version(self):
	"""Returns the witness version on [0,16]. """
	return next(iter(self))

Because the witness version is actually a 'small int' opcode - that is, for witness version 1, without decode_op_n(), the returned value will be 0x51. It worked for version 0 because 'small int' opcode is decoded as 0 --> 0; 0x51..0x60 --> 1..16