R1:8d128646b31a

Fix a lisk issue

Summary:
This was broken in D12680.

```
EXCEPTION: (PhutilJSONParserException) Parse error on line 0 at column 0: 'null' is not a valid JSON object. at [<phutil>/src/parser/PhutilJSONParser.php:41]
#0 PhutilJSONParser::parse(string) called at [<phutil>/src/utils/utils.php:1062]
#1 phutil_json_decode(string) called at [<phabricator>/src/infrastructure/storage/lisk/LiskDAO.php:1640]
#2 LiskDAO::applyLiskDataSerialization(array, boolean) called at…