Cannot read property 'title' of undefined

[iamsonivivek]

Warning: Each child in an array or iterator should have a unique "key" prop. Check the render method of Post. See https://fb.me/react-warning-keys for more information.
Warning: No route matches path "/static/client.js". Make sure you have somewhere in your routes
TypeError: Cannot read property 'title' of undefined
at Function. (/home/yuva/Downloads/react-helmet-example-master/server.js:45:34)
at Function.dispatchHandler (/home/yuva/Downloads/react-helmet-example-master/node_modules/react-router/lib/createRouter.js:379:22)
at /home/yuva/Downloads/react-helmet-example-master/node_modules/react-router/lib/createRouter.js:347:29
at Function.Transition.to (/home/yuva/Downloads/react-helmet-example-master/node_modules/react-router/lib/Transition.js:72:15)
at /home/yuva/Downloads/react-helmet-example-master/node_modules/react-router/lib/createRouter.js:346:22
at Function.Transition.from (/home/yuva/Downloads/react-helmet-example-master/node_modules/react-router/lib/Transition.js:51:15)
at Function.dispatch (/home/yuva/Downloads/react-helmet-example-master/node_modules/react-router/lib/createRouter.js:343:20)
at Function.refresh (/home/yuva/Downloads/react-helmet-example-master/node_modules/react-router/lib/createRouter.js:394:16)
at Function.run (/home/yuva/Downloads/react-helmet-example-master/node_modules/react-router/lib/createRouter.js:390:16)
at /home/yuva/Downloads/react-helmet-example-master/server.js:24:12