Fix studio link command

Nuxeo CLI             : 1.8.4
Modules
 - generator-nuxeo    : 2.8.1 
 - yeoman-environment : 2.3.3

$ nuxeo studio link
? NOS Username: zgcnxgml@abyssmail.com
? NOS Password: [hidden]
? Studio Project: tests-studio1
? Do you want to update your Maven settings.xml file accordingly? Yes

events.js:160
      throw er; // Unhandled 'error' event
      ^


Error: Unable to read Maven Coordonates for tests-studio1
    at constructor._getProjectMavenCoordonates (/home/bert/.npm-global/lib/node_modules/nuxeo-cli/node_modules/generator-nuxeo/generators/studio/studio.js:34:13)
    at spinner (/home/bert/.npm-global/lib/node_modules/nuxeo-cli/node_modules/generator-nuxeo/generators/studio/link-delegate.js:82:19)
    at module.exports (/home/bert/.npm-global/lib/node_modules/nuxeo-cli/node_modules/generator-nuxeo/utils/spinner.js:11:12)
    at constructor.writing (/home/bert/.npm-global/lib/node_modules/nuxeo-cli/node_modules/generator-nuxeo/generators/studio/link-delegate.js:81:17)
    at delegate (/home/bert/.npm-global/lib/node_modules/nuxeo-cli/node_modules/generator-nuxeo/lib/delegated-generator.js:92:31)
    at constructor.writing (/home/bert/.npm-global/lib/node_modules/nuxeo-cli/node_modules/generator-nuxeo/lib/delegated-generator.js:73:7)
    at Object.<anonymous> (/home/bert/.npm-global/lib/node_modules/nuxeo-cli/node_modules/yeoman-generator/lib/index.js:417:23)
    at /home/bert/.npm-global/lib/node_modules/nuxeo-cli/node_modules/run-async/index.js:25:25
    at /home/bert/.npm-global/lib/node_modules/nuxeo-cli/node_modules/run-async/index.js:24:19