Started with `localstack start` then navigated to `http://localhost:4569/shell`

Localstack version is `0.10.5`

![Screenshot from 2019-11-26 08-15-03](https://user-images.githubusercontent.com/57932946/69588919-24798700-1025-11ea-94d2-9cfb6dd20004.png)

Console log below, its all the same so I am just posting one

```2019-11-26T00:13:18:ERROR:localstack.services.generic_proxy: Error forwarding request: the JSON object must be str, bytes or bytearray, not NoneType Traceback (most recent call last):
  File "/opt/code/localstack/localstack/services/generic_proxy.py", line 240, in forward
    path=path, data=data, headers=forward_headers)
  File "/opt/code/localstack/localstack/services/dynamodb/dynamodb_listener.py", line 44, in forward_request
    data = json.loads(to_str(data))
  File "/usr/lib/python3.7/json/__init__.py", line 341, in loads
    raise TypeError(f'the JSON object must be str, bytes or bytearray, '
TypeError: the JSON object must be str, bytes or bytearray, not NoneType```

import re
import json
import random
import logging
import threading
from binascii import crc32
from requests.models import Response
from localstack import config
from localstack.utils.aws import aws_stack
from localstack.utils.common import to_bytes, to_str, clone
from localstack.utils.analytics import event_publisher
from localstack.services.awslambda import lambda_api
from localstack.services.generic_proxy import ProxyListener
from localstack.services.dynamodbstreams import dynamodbstreams_api
TABLE_DEFINITIONS = {}
ACTION_PREFIX = 'DynamoDB_20120810'
LOGGER = logging.getLogger(__name__)
THROTTLED_ACTIONS = [
    'PutItem', 'BatchWriteItem', 'UpdateItem', 'DeleteItem', 'TransactWriteItems',
    'GetItem', 'Query', 'Scan', 'TransactGetItems', 'BatchGetItem'
]
class ProxyListenerDynamoDB(ProxyListener):
    thread_local = threading.local()
    def __init__(self):