##### SUMMARY
The delete operation of the `lightsail` module is not idempotent. If the instance is already deleted, then the task generates a traceback.

```
Traceback (most recent call last):
  File "ansible/modules/cloud/amazon/lightsail.py", line 458, in main
  File "ansible/modules/cloud/amazon/lightsail.py", line 422, in core
  File "ansible/module_utils/common/dict_transformations.py", line 42, in camel_dict_to_snake_dict
    for k, v in camel_dict.items():
AttributeError: 'NoneType' object has no attribute 'items'
```

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
`lightsail`

##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```paste below
ansible 2.10.0.dev0
```

##### CONFIGURATION
<!--- Paste verbatim output from "ansible-config dump --only-changed" between quotes -->
```paste below
nothing
```

##### OS / ENVIRONMENT
<!--- Provide all relevant information below, e.g. target OS versions, network device firmware, etc. -->
Python 3.7.4

##### STEPS TO REPRODUCE
<!--- Describe exactly how to reproduce the problem, using a minimal test-case -->

<!--- Paste example playbooks or commands between quotes below -->
```yaml
- lightsail:
    state: absent
    name: my_instance
```

##### EXPECTED RESULTS
<!--- Describe what you expected to happen when running the steps above -->
Task successfully returns with `changed: false`.

##### ACTUAL RESULTS
<!--- Describe what actually happened. If possible run with extra verbosity (-vvvv) -->
Instead this traceback is generated - 
<!--- Paste verbatim command output between quotes -->
```paste below
Traceback (most recent call last):
  File "ansible/modules/cloud/amazon/lightsail.py", line 458, in main
  File "ansible/modules/cloud/amazon/lightsail.py", line 422, in core
  File "ansible/module_utils/common/dict_transformations.py", line 42, in camel_dict_to_snake_dict
    for k, v in camel_dict.items():
AttributeError: 'NoneType' object has no attribute 'items'

```

blueprintId=blueprint_id,
                bundleId=bundle_id,
                userData=user_data,
                keyPairName=key_pair_name,
            )
            resp = resp['operations'][0]
        except botocore.exceptions.ClientError as e:
            module.fail_json(msg='Unable to create instance {0}, error: {1}'.format(instance_name, e))
        changed = True
    inst = _find_instance_info(client, instance_name)
    return (changed, inst)
def delete_instance(module, client, instance_name):
    """
    Terminates an instance
    module: Ansible module object
    client: authenticated lightsail connection object
    instance_name: name of instance to delete
    Returns a dictionary of instance information
    about the instance deleted (pre-deletion).
    If the instance to be deleted is running
    "changed" will be set to False.
    """
    
    wait = module.params.get('wait')
    wait_timeout = int(module.params.get('wait_timeout'))
    wait_max = time.time() + wait_timeout
    changed = False
    inst = None
    try:
        inst = _find_instance_info(client, instance_name)