How to ignore missing parameters in Groovy's template engine

I have a template with placeholders(e.x. ${PARAM1}), the program successfully resolves them. But what to do if I want to resolve only placeholders which I pass to template engine and leave other ${} ignored? Currently the program fails if it can't resolve all placeholders.

static void main(String[] args) {

    def template = this.getClass().getResource('/MyFile.txt').text

    def parameters = [
        "PARAM1": "VALUE1",
        "PARAM2": "VALUE2"
    ]
    def templateEngine = new SimpleTemplateEngine()
    def output = templateEngine.createTemplate(template).make(parameters)
    print output
}

File: ${PARAM1} ${PARAM2} ${PARAM3}

Thanks