ReferenceError: navigator is not defined

[reggi]

/Users/thomas/Desktop/shopify-react/node_modules/react-router/modules/utils/supportsHistory.js:7
  var ua = navigator.userAgent;
           ^
ReferenceError: navigator is not defined
    at supportsHistory (/Users/thomas/Desktop/shopify-react/node_modules/react-router/modules/utils/supportsHistory.js:7:12)
    at createRouter (/Users/thomas/Desktop/shopify-react/node_modules/react-router/modules/utils/createRouter.js:159:40)
    at Object.runRouter [as run] (/Users/thomas/Desktop/shopify-react/node_modules/react-router/modules/utils/runRouter.js:38:16)
    at Object.<anonymous> (/Users/thomas/Desktop/shopify-react/react/App.react.js:14:8)
    at Module._compile (module.js:456:26)
    at Object.require.extensions.(anonymous function) [as .js] (/Users/thomas/Desktop/shopify-react/node_modules/node-jsx/index.js:26:12)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Module.require (module.js:364:17)
    at require (module.js:380:17)