buildStatic and conditional boolean true with rollup enabled in jspm@beta

Hello, when I try to compile with conditional boolean in true and rollup enabled I am getting follow error:

 Error: TypeError: Error compiling esm module "@dummy-entry-point" at null
        Path must be a string. Received null
    at builder.buildStatic.then.catch (/Users/horasikus/work_latest/conditional/gulpfile.js:19:35)
    at tryCatcher (/Users/horasikus/work_latest/conditional/node_modules/bluebird/js/release/util.js:16:23)
    at Promise._settlePromiseFromHandler (/Users/horasikus/work_latest/conditional/node_modules/bluebird/js/release/promise.js:512:31)
    at Promise._settlePromise 
...

I already checked similar issues 339 and 549 but it seems a new issue because now ENV is well resolved only throwing this exception when the condition is true. If i disable rollup the bundle is ok.

src/env.conditions.js (it is not used by the builder static, only for dev mode)

export var mock = true;

jspm.config.js

SystemJS.config({
    map: {
        "ENV": "src/env.conditions.js"
    },
    nodeConfig: {
        "paths": {
            "npm:": "jspm_packages/npm/"
        }
    },
    devConfig: {
        "map": {
            "plugin-babel": "npm:systemjs-plugin-babel@0.0.25"
        }
    },
    packages: {
        "src": {
            "format": "esm",
            "meta": {
                "*.js": {
                    "loader": "plugin-babel"
                }
            }
        }
    }
});

src/app.js

import './employee.mock.js#?ENV|mock';

src/employee.mock.js

export default name = 'foo';

gulpfile.js

gulp.task('bundle', (cb) => {
    const Builder = require('systemjs-builder');
    const builder = new Builder();
    const inputPath = 'src/app.js';
    const outputFile = `dist/app.js`;
    const outputOptions = {
        conditions: {
            'ENV|mock.js': true
        },
        rollup: true
    };

    builder.loadConfig('jspm.config.js')
        .then(() => {
            builder.buildStatic(inputPath, outputFile, outputOptions)
                .then(() => cb())
                .catch((ex) => cb(new Error(ex)));
        });
});

package.json

{
  "name": "conditional",
  "version": "0.0.0",
  "description": "",
  "jspm": {
    "devDependencies": {
      "plugin-babel": "npm:systemjs-plugin-babel@^0.0.25"
    }
  },
  "dependencies": {
    "systemjs-builder": "^0.16.9"
  }
}

I tried command line with the same results. I'm using latest jspm 0.17.0-beta.42.

This issue only happens building the static bundle; jspm+systemjs in dev mode (load modules as separate files with ES6 in the browser) work as expected (playing with the condition in src/env.conditions.js). Also only fails with output format is esm.

systemjs / builder

buildStatic and conditional boolean true with rollup enabled in jspm@beta #831