Can't deploy hybridRunbookWorkerGroups without error

**Bicep version**
run `bicep --version` via the Bicep CLI, `az bicep version` via the AZ CLI or via VS code by navigating to the extensions tab and searching for Bicep

Bicep CLI version 0.4.1008 (223b8d227a)

**Describe the bug**
I am trying to deploy a hybrid worker group, hybrid worker, and then deploy the hybrid extension to a basic windows VM. When I go to run this code, The group successfully creates but throws an error.

```bicep
resource hybrid_worker_group 'Microsoft.Automation/automationAccounts/hybridRunbookWorkerGroups@2021-06-22' = {
name: 'HybridGroup1'
parent: automation_test_acct
dependsOn:[automation_credential
]
}
```

Error message

```
{"status":"Failed","error":{"code":"DeploymentFailed","message":"At least one resource deployment operation failed. Please list deployment operations for details. Please see https://aka.ms/DeployOperations for usage details.","details":[{"code":"InternalServerError","message":"{\r\n \"error\": {\r\n \"code\": \"ResourceDeploymentFailure\",\r\n \"message\": \"The response for resource had empty or invalid content.\"\r\n }\r\n}"}]}}
```

Raw error
```
{
"code": "DeploymentFailed",
"message": "At least one resource deployment operation failed. Please list deployment operations for details. Please see https://aka.ms/DeployOperations for usage details.",
"details": [
{
"code": "ResourceDeploymentFailure",
"message": "The response for resource had empty or invalid content."
}
]
}
```

So looking at the provider documentation here - https://docs.microsoft.com/en-us/azure/templates/microsoft.automation/2021-06-22/automationaccounts/hybridrunbookworkergroups?tabs=bicep#runascredentialassociationproperty

I need to reference a credential block. I do not need to do this in the portal though and it can be blank. I have tried just including a blank credential block, omitting the block and for the heck of it, deploying a credential and then referencing the credential in multiple ways (static name, referencing credential_test.name, credential_test.property.description) and then I get this error

```bicep
resource automation_credential 'Microsoft.Automation/automationAccounts/credentials@2020-01-13-preview' = {
name: 'unused'
parent: automation_test_acct
properties: {
description: 'unused'
password: 'username'
userName: 'password123'
}
}

output output2 string = automation_credential.name

resource hybrid_worker_group 'Microsoft.Automation/automationAccounts/hybridRunbookWorkerGroups@2021-06-22' = {
name: 'HybridGroup1'
parent: automation_test_acct
credential: {
name: automation_credential.properties.description
}
dependsOn:[automation_credential
]
}
```

```
{"status":"Failed","error":{"code":"DeploymentFailed","message":"At least one resource deployment operation failed. Please list deployment operations for details. Please see https://aka.ms/DeployOperations for usage details.","details":[{"code":"InternalServerError","message":"{\r\n \"error\": {\r\n \"code\": \"ResourceDeploymentFailure\",\r\n \"message\": \"The response for resource had empty or invalid content.\"\r\n }\r\n}"}]}}
```

**Additional context**
I know this feature is in preview but trying to see if this is a problem with my bicep code or from what I can tell appears to be potentially a bug. any help is appreciated!

Reproduce the deployment using the shown hybridRunbookWorkerGroups Bicep resource and the listed Bicep CLI or Azure CLI commands. Inspect the deployment operations referenced by aka.ms/DeployOperations, comparing cases with no credential block, a blank block, and a credential reference. Done means the hybrid worker group deploys without the empty or invalid content error.

Written by the indexing model from the issue text.