Can't add email reciever to acrion group

intial create was: az monitor action-group create --name krcli4 -g resgroup --action email tellErrors kevin@somewhere.com
tried to add a second email addrees (which failed) : az monitor action-group update --name krcli4 -g resgroup --add emailReceivers tellErrors2 kevin2@somewhere.com

diagnostics are:

Enter the number of the command you would like to create an issue for. Enter q to quit: INFO:
### **This is autogenerated. Please review and update as needed.**

## Describe the bug

**Command Name**
`az monitor action-group update`

**Errors:**
```
The command failed with an unexpected error. Here is the traceback:
Unable to build a model: Unable to deserialize to object: type, AttributeError: 'str' object has no attribute 'get', DeserializationError: Unable to deserialize to object: type, AttributeError: 'str' object has no attribute 'get'
Traceback (most recent call last):
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/serialization.py", line 1428, in _deserialize
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/serialization.py", line 1193, in rest_key_case_insensitive_extractor
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/serialization.py", line 1222, in attribute_key_case_insensitive_extractor
AttributeError: 'str' object has no attribute 'get'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/serialization.py", line 620, in body
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/serialization.py", line 1398, in _deserialize
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/serialization.py", line 1407, in _deserialize
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/serialization.py", line 1618, in deserialize_data
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/serialization.py", line 1649, in deserialize_iter
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/serialization.py", line 1649, in
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/serialization.py", line 1631, in deserialize_data
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/serialization.py", line 1446, in _deserialize
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/exceptions.py", line 51, in raise_with_traceback
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/serialization.py", line 1428, in _deserialize
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/serialization.py", line 1193, in rest_key_case_insensitive_extractor
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/serialization.py", line 1222, in attribute_key_case_insensitive_extractor
msrest.exceptions.DeserializationError: Unable to deserialize to object: type, AttributeError: 'str' object has no attribute 'get'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\knack/cli.py", line 231, in invoke
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/core/commands/__init__.py", line 657, in execute
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/core/commands/__init__.py", line 720, in _run_jobs_serially
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/core/commands/__init__.py", line 712, in _run_job
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/command_modules/monitor/_exception_handler.py", line 23, in exception_handler
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/core/commands/__init__.py", line 691, in _run_job
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/core/commands/__init__.py", line 328, in __call__
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/core/commands/command_operation.py", line 242, in handler
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/core/commands/__init__.py", line 447, in cached_put
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/cli/core/commands/__init__.py", line 441, in _put_operation
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\azure/mgmt/monitor/v2019_06_01/operations/_action_groups_operations.py", line 97, in create_or_update
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/serialization.py", line 622, in body
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/exceptions.py", line 51, in raise_with_traceback
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/serialization.py", line 620, in body
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/serialization.py", line 1398, in _deserialize
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/serialization.py", line 1407, in _deserialize
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/serialization.py", line 1618, in deserialize_data
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/serialization.py", line 1649, in deserialize_iter
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/serialization.py", line 1649, in
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/serialization.py", line 1631, in deserialize_data
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/serialization.py", line 1446, in _deserialize
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/exceptions.py", line 51, in raise_with_traceback
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/serialization.py", line 1428, in _deserialize
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/serialization.py", line 1193, in rest_key_case_insensitive_extractor
File "D:\a\1\s\build_scripts\windows\artifacts\cli\Lib\site-packages\msrest/serialization.py", line 1222, in attribute_key_case_insensitive_extractor
msrest.exceptions.SerializationError: Unable to build a model: Unable to deserialize to object: type, AttributeError: 'str' object has no attribute 'get', DeserializationError: Unable to deserialize to object: type, AttributeError: 'str' object has no attribute 'get'

```

## 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 monitor action-group update --name {} -g {} --add {} {} {}`

## Expected Behavior

## Environment Summary
```
Windows-10-10.0.18362-SP0
Python 3.8.9
Installer: MSI

azure-cli 2.28.0

Extensions:
logic 0.1.4
storage-preview 0.7.1

```
## Additional Context

INFO: Command ran in 5.706 seconds (init: 0.961, invoke: 4.745)