Crash fix.

libethereum/Executive.cpp

@@ -396,9 +396,8 @@ void Executive::finalize()
 
 	// SSTORE refunds...
 	// must be done before the miner gets the fees.
-	m_refunded = min((m_t.gas() - m_gas) / 2, m_ext->sub.refunds);
-	if (m_ext)
-		m_gas += m_refunded;
+	m_refunded = m_ext ? min((m_t.gas() - m_gas) / 2, m_ext->sub.refunds) : 0;
+	m_gas += m_refunded;
 
 	//	cnote << "Refunding" << formatBalance(m_endGas * m_ext->gasPrice) << "to origin (=" << m_endGas << "*" << formatBalance(m_ext->gasPrice) << ")";
 	m_s.addBalance(m_t.sender(), m_gas * m_t.gasPrice());