fix vm web3 provider

src/storage/storageResolver.js

@@ -110,7 +110,7 @@ function toCache (self, address, storage) {
 
 function storageRangeWeb3Call (tx, address, start, maxSize, callback) {
   if (traceHelper.isContractCreation(address)) {
-    callback(null, {}, true)
+    callback(null, {}, null)
   } else {
     util.web3.debug.storageRangeAt(
       tx.blockHash, tx.transactionIndex === undefined ? tx.hash : tx.transactionIndex,

src/web3Provider/web3VmProvider.js

@@ -158,8 +158,8 @@ web3VmProvider.prototype.storageRangeAt = function (blockNumber, txIndex, addres
   if (this.storageCache[txIndex] && this.storageCache[txIndex][address]) {
     var storage = this.storageCache[txIndex][address]
     return cb(null, {
-      storage: JSON.parse(JSON.stringify(storage)), // copy
-      complete: true
+      storage: Object.assign({}, storage),
+      nextKey: null
     })
   } else {
     cb('unable to retrieve storage ' + txIndex + ' ' + address)