Fix a bug on empty NODE_PATH (#2264)

Author: gaearon

Diff for: packages/react-scripts/config/webpack.config.dev.js

@@ -88,7 +88,7 @@ module.exports = {
     // https://github.com/facebookincubator/create-react-app/issues/253
     modules: ['node_modules', paths.appNodeModules].concat(
       // It is guaranteed to exist because we tweak it in `env.js`
-      process.env.NODE_PATH.split(path.delimiter)
+      process.env.NODE_PATH.split(path.delimiter).filter(Boolean)
     ),
     // These are the reasonable defaults supported by the Node ecosystem.
     // We also include JSX as a common component filename extension to support

Diff for: packages/react-scripts/config/webpack.config.prod.js

@@ -86,7 +86,7 @@ module.exports = {
     // https://github.com/facebookincubator/create-react-app/issues/253
     modules: ['node_modules', paths.appNodeModules].concat(
       // It is guaranteed to exist because we tweak it in `env.js`
-      process.env.NODE_PATH.split(path.delimiter)
+      process.env.NODE_PATH.split(path.delimiter).filter(Boolean)
     ),
     // These are the reasonable defaults supported by the Node ecosystem.
     // We also include JSX as a common component filename extension to support