[Bug] Could not queue the build because there were validation errors or warnings.

I am trying to use the new version:

```
- uses: Azure/pipelines@v1.2
with:
azure-devops-project-url: 'https://dev.azure.com/organization/project-name'
azure-pipeline-name: 'pipeline-name' # name of the Azure pipeline to be triggered
azure-devops-token: '${{ secrets.AZURE_DEVOPS_TOKEN }}'
azure-pipeline-variables: '{"variable1": "value1", "variable2": "value2"}' # optional stringified json
```

but once I create the workflow in which I pass some variables I get the following message:

**Error: Could not queue the build because there were validation errors or warnings.**

Are those not supported yet?

Removing the following section from my workflow definition, the pipeline get triggered.

` azure-pipeline-variables: '{"variable1": "value1", "variable2": "value2"}' # optional stringified json
`