Custom monitoring signal examples not working

### Operating System

Windows

### Version Information

azure-cli: 2.53.0
azure-cli-core: 2.53.0
azure-cli-telemetry: 1.1.0
extensions:
ml: 2.21.0

### Steps to reproduce

1. Follow instruction for [5. Create your own custom monitoring signal in /cli/monitoring](https://github.com/Azure/azureml-examples/tree/main/cli/monitoring#5-create-your-own-custom-monitoring-signal)

### Expected behavior

Expected: A custom signal monitor is created and viewable from the Azure Machine Learning workspace monitoring dashboard

### Actual behavior

CLI returns `Met error :'NoneType' object has no attribute 'values'`

### Addition information

Adding an `inputs` field to `custom_monitoring.yaml` changes the error message to `Met error :`

```
# custom-monitoring.yaml
$schema: http://azureml/sdk-2-0/Schedule.json
name: my-custom-signal
trigger:
type: recurrence
frequency: day # can be minute, hour, day, week, month
interval: 7 # #every day
create_monitor:
compute:
instance_type: "standard_e8s_v3"
runtime_version: "3.2"
monitoring_signals:
customSignal:
type: custom
component_id: azureml:my_custom_signal:1.0.0
inputs: # this is new
input_1:
input_data:
type: mltable
path: azureml:Direct:1
data_context: test
input_data:
test_data_1:
input_data:
type: mltable
path: azureml:Direct:1
data_context: test
test_data_2:
input_data:
type: mltable
path: azureml:Direct:1
data_context: test
data_window:
trailing_window_size: P30D
trailing_window_offset: P7D
pre_processing_component: azureml:custom_preprocessor:1.0.0
metric_thresholds:
- metric_name: std_dev
threshold: 2
alert_notification:
emails:
- abc@example.com
```

Start by reproducing the linked `/cli/monitoring` example on Windows with `custom-monitoring.yaml`, including the reported configuration variants. Inspect the example configuration and CLI invocation to identify why creation fails; done means the custom signal is created successfully and appears in the Azure Machine Learning workspace monitoring dashboard without either error.

Written by the indexing model from the issue text.