spinnaker: Pipeline can not resolve ${ templateVariables.env } if triggered by another pipeline

Issue Summary:

I have a pipeline which is created by pipeline-template, and it has a variable which is rendered by ${ templateVariables.env }. It run well while it is triggered by manual, however, if I trigger this pipeline by using Runs a pipeline, then it will fail.

Cloud Provider(s):

Kubernetes v2

Environment:

1.15.0

Steps to Reproduce:

1. Create pipeline A by pipeline template, and this pipeline has the value render by templateVariables
2. Create another pipeline B with Runs a pipeline to trigger the pipeline A.
3. Start pipelineB manually, then failed

Additional Details:

Trigger manually

# source
overrides: {
  env: "stg"
}

Trigger by other pipeline

# source
overrides: {
env: "${ templateVariables.env }"
}

# log
expressionEvaluationSummary: {
  templateVariables.env: [
    {
      description: "Failed to evaluate [env] EL1007E: Property or field 'env' cannot be found on null",
      exceptionType: "org.springframework.expression.spel.SpelEvaluationException",
      timestamp: 1563861343095,
      level: "ERROR"
    }
  ]
}