Request Transformer Issue

Questions
1

I am running Kong 0.14 and trying the request transformer plugin however it gives me HTTP Error 500 during my POST request. I can confirm the Content-Type and Accept is application/json. The nginx error log shows:

2018/08/21 20:07:51 [error] 110969#0: *198403 lua coroutine: runtime error: ...hare/lua/5.1/kong/plugins/request-transformer/access.lua:218: attempt to index local 'parameters' (a nil value)
stack traceback:
coroutine 0:
        ...hare/lua/5.1/kong/plugins/request-transformer/access.lua: in function 'transform_json_body'
        ...hare/lua/5.1/kong/plugins/request-transformer/access.lua:355: in function 'transform_body'
        ...hare/lua/5.1/kong/plugins/request-transformer/access.lua:391: in function 'execute'
        ...are/lua/5.1/kong/plugins/request-transformer/handler.lua:12: in function <...are/lua/5.1/kong/plugins/request-transformer/handler.lua:10>
coroutine 1:
        [C]: in function 'resume'
        coroutine.wrap:21: in function <coroutine.wrap:21>
        /usr/local/share/lua/5.1/kong/init.lua:468: in function 'access'

It seems like it is accessing parameters parsed from the json body. Digging through the access.lua code for request transformer plugin, this is not supposed to happen as there is already a nil check at the beginning of transform_json_body. The error 500 happens when add body is set. When only replace body is set, the value parameter cust_client_id is not replaced to a new value also. I may have configuration issue. Can someone please confirm?

Here is the file transformer configuration:

{
“created_at”: 1534856800000,
“config”: {
“remove”: {
“querystring”: {},
“headers”: {},
“body”: {}
},
“append”: {
“querystring”: {},
“headers”: {},
“body”: {}
},
“replace”: {
“querystring”: {},
“headers”: {},
“body”: [
“cust_client_id:MANTAP”
]
},
“add”: {
“querystring”: {},
“headers”: {},
“body”: [
“cust_client_id:MANTAP”
]
},
“rename”: {
“querystring”: {},
“headers”: {},
“body”: {}
}
},
“id”: “033079c0-57f0-4e5c-914f-caf0768db6cf”,
“route_id”: “a75c5613-681b-493c-9d8b-a5d4e3c7749e”,
“name”: “request-transformer”,
“enabled”: true,
“consumer_id”: “f2cde232-e432-423c-bc2f-60eb84c2a71a”
}