message: test: add `bad-txns-prevout-null` test case to invalid_txs.py
  This reject reason is triggered for non-coinbase transactions with
  a coinbase-like outpoint, i.e. hash=0, n=0xffffffff.
  Note that the invalid tx templates are currently used in the
  functional tests feature_block.py and p2p_invalid_tx.py.
diff: @@ -151,6 +151,19 @@ class DuplicateInput(BadTxTemplate):
  return tx
  +class PrevoutNullInput(BadTxTemplate):
  + reject_reason = 'bad-txns-prevout-null'
  + expect_disconnect = True
  +
  + def get_tx(self):
  + tx = CTransaction()
  + tx.vin.append(self.valid_txin)
  + tx.vin.append(CTxIn(COutPoint(hash=0, n=0xffffffff)))
  + tx.vout.append(CTxOut(1, basic_p2sh))
  + tx.calc_sha256()
  + return tx
  +
  +
  class NonexistentInput(BadTxTemplate):
  reject_reason = None # Added as an orphan tx.
  expect_disconnect = False
  