Merge pull request #14 from han0110/fix/missing-refund-change-journal

Fix: add missing `refundChange` to journal

minigeth/core/state/statedb.go

@@ -202,12 +202,14 @@ func (s *StateDB) Preimages() map[common.Hash][]byte {
 
 // AddRefund adds gas to the refund counter
 func (s *StateDB) AddRefund(gas uint64) {
+	s.journal.append(refundChange{prev: s.refund})
 	s.refund += gas
 }
 
 // SubRefund removes gas from the refund counter.
 // This method will panic if the refund counter goes below zero
 func (s *StateDB) SubRefund(gas uint64) {
+	s.journal.append(refundChange{prev: s.refund})
 	if gas > s.refund {
 		panic(fmt.Sprintf("Refund counter below zero (gas: %d > refund: %d)", gas, s.refund))
 	}