Defect: TerraformEnvironment.nextStage syntax error

[kmanning]

To reproduce:

1. Create a pipeline without a ValidateStage, only TerraformEnvironmentStages.
2. Call .then on the TerraformEnvironmentStage

def deployIntegration = new TerraformEnvironmentStage('integration')
def deployProduction= new TerraformEnvironmentStage('production')

deployIntegration.then(deployProduction)
        .build()

Expected
It creates a pipeline, starting with the TerraformEnvironmentStage

Actual
It throws an error:
No such property: nextStage

[kmanning]

Merged into v5.5-dev