core/state: fix ripemd-cornercase in Copy

Author: holiman

core/state/statedb.go

@@ -471,8 +471,14 @@ func (self *StateDB) Copy() *StateDB {
 	}
 	// Copy the dirty states, logs, and preimages
 	for addr := range self.journal.dirties {
-		state.stateObjects[addr] = self.stateObjects[addr].deepCopy(state)
-		state.stateObjectsDirty[addr] = struct{}{}
+		// As documented [here](https://github.com/ethereum/go-ethereum/pull/16485#issuecomment-380438527),
+		// and in the Finalise-method, there is a case where an object is in the journal but not
+		// in the stateObjects: OOG after touch on ripeMD prior to Byzantium. Thus, we need to check for
+		// nil
+		if object, exist := self.stateObjects[addr]; exist {
+			state.stateObjects[addr] = object.deepCopy(state)
+			state.stateObjectsDirty[addr] = struct{}{}
+		}
 	}
 	// Above, we don't copy the actual journal. This means that if the copy is copied, the
 	// loop above will be a no-op, since the copy's journal is empty.