Error when trying to get VMSS instance connection info in Azure CLI

### **This is autogenerated. Please review and update as needed.**

## Describe the bug

**Command Name**
`az vmss list-instance-connection-info`

**Errors:**
```
'NoneType' object has no attribute 'id'
Traceback (most recent call last):
python3.6/site-packages/knack/cli.py, ln 215, in invoke
cmd_result = self.invocation.execute(args)
cli/core/commands/__init__.py, ln 654, in execute
raise ex
cli/core/commands/__init__.py, ln 717, in _run_jobs_serially
results.append(self._run_job(expanded_arg, cmd_copy))
...
azure/cli/core/__init__.py, ln 784, in default_command_handler
return op(**command_args)
cli/command_modules/vm/custom.py, ln 2769, in list_vmss_instance_connection_info
instance_id = parse_resource_id(rule.backend_ip_configuration.id)['child_name_1']
AttributeError: 'NoneType' object has no attribute 'id'
```

## To Reproduce:
Steps to reproduce the behavior. Note that argument values have been redacted, as they may contain sensitive information.

- _Put any pre-requisite steps here..._
- `az vmss list-instance-connection-info -g {} -n {}`

## Expected Behavior

## Environment Summary
```
Linux-4.4.0-19041-Microsoft-x86_64-with-debian-bullseye-sid
Python 3.6.10
Installer: DEB

azure-cli 2.15.1

Extensions:
image-copy-extension 0.2.1
maintenance 1.0.1
vm-repair 0.3.1

```
## Additional Context