##### 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'

```

"""
    Reboot an existing instance
    module: Ansible module object
    client: authenticated lightsail connection object
    instance_name: name of instance to reboot
    Returns a dictionary of instance information
    about the restarted instance
    If the instance was not able to reboot,
    "changed" will be set to False.
    Wait will not apply here as this is an OS-level operation
    """
    wait = module.params.get('wait')
    wait_timeout = int(module.params.get('wait_timeout'))
    wait_max = time.time() + wait_timeout