Alter "" to null.

TrieTests/trietest.json

@@ -6,9 +6,9 @@
       ["horse", "stallion"],
       ["shaman", "horse"],
       ["doge", "coin"],
-      ["ether", ""],
+      ["ether", null],
       ["dog", "puppy"],
-      ["shaman", ""]
+      ["shaman", null]
     ],
     "root": "0x5991bb8c6514148a29db676a14ac506cd2cd5775ace63c30a4fe457715e9ac84"
   },
@@ -22,7 +22,7 @@
       ["0x000000000000000000000000ec4f34c97e43fbb2816cfd95e388353c7181dab1", "0x4e616d6552656700000000000000000000000000000000000000000000000000"],
       ["0x4655474156000000000000000000000000000000000000000000000000000000", "0x7ef9e639e2733cb34e4dfc576d4b23f72db776b2"],
       ["0x4e616d6552656700000000000000000000000000000000000000000000000000", "0xec4f34c97e43fbb2816cfd95e388353c7181dab1"],
-      ["0x0000000000000000000000000000000000000000000000000000001234567890", ""],
+      ["0x0000000000000000000000000000000000000000000000000000001234567890", null],
       ["0x000000000000000000000000697c7b8c961b56f675d570498424ac8de1a918f6", "0x6f6f6f6820736f2067726561742c207265616c6c6c793f000000000000000000"],
       ["0x6f6f6f6820736f2067726561742c207265616c6c6c793f000000000000000000", "0x697c7b8c961b56f675d570498424ac8de1a918f6"]
     ],