Error: Cannot read property 'split' of undefined

[henrinormak]

With nested functions/definitions, an error occurs when the inner value is not defined on the parameters/payload.

Minimal example that causes this problem:

var mappingTemplate = require('api-gateway-mapping-template');

var template = '$util.escapeJavaScript($input.params(\'test\'))';

var params = {
    header: {},
    querystring: {},
    path: {}
};
var payload = '';

var result = mappingTemplate({
    template: template,
    params: params
    payload: payload
});

// Results in error similar to
// Error: Cannot read property 'split' of undefined on $util.escapeJavaScript($input.params('test')) at L/N 1:0

Expected behavior (and as far as I understand, what API Gateway would actually do) is to resolve this to be completely undefined, meaning calls to util functions with an undefined parameter results in an undefined value.