Getting cryptic error if the file to return ENV object return null or {} instead

I have solved the issue myself but I thought it can be better.

It is good that it throws an error about it but the cryptic error message like this is not helping
```
remote: Module build failed: TypeError: /tmp/build_43fb00b7ca544651b6eb4730c0d0ad94/components/BuildTeam.js: Cannot convert undefined or null to object
remote: at PluginPass.UnaryExpression (/tmp/build_43fb00b7ca544651b6eb4730c0d0ad94/node_modules/babel-plugin-transform-define/lib/index.js:34:27)
remote: at newFn (/tmp/build_43fb00b7ca544651b6eb4730c0d0ad94/node_modules/babel-traverse/lib/visitors.js:276:21)
remote: at NodePath._call (/tmp/build_43fb00b7ca544651b6eb4730c0d0ad94/node_modules/babel-traverse/lib/path/context.js:76:18)
remote: at NodePath.call (/tmp/build_43fb00b7ca544651b6eb4730c0d0ad94/node_modules/babel-traverse/lib/path/context.js:48:17)
remote: at NodePath.visit (/tmp/build_43fb00b7ca544651b6eb4730c0d0ad94/node_modules/babel-traverse/lib/path/context.js:105:12)
remote: at TraversalContext.visitQueue (/tmp/build_43fb00b7ca544651b6eb4730c0d0ad94/node_modules/babel-traverse/lib/context.js:150:16)
remote: at TraversalContext.visitSingle (/tmp/build_43fb00b7ca544651b6eb4730c0d0ad94/node_modules/babel-traverse/lib/context.js:108:19)
remote: at TraversalContext.visit (/tmp/build_43fb00b7ca544651b6eb4730c0d0ad94/node_modules/babel-traverse/lib/context.js:192:19)
remote: at Function.traverse.node (/tmp/build_43fb00b7ca544651b6eb4730c0d0ad94/node_modules/babel-traverse/lib/index.js:114:17)
remote: at NodePath.visit (/tmp/build_43fb00b7ca544651b6eb4730c0d0ad94/node_modules/babel-traverse/lib/path/context.js:115:19)
```
This throws when the page it is saying at fault does not even use any of the variables supposed to be defined in env, but simply uses Unary Expression like "typeof".

Perhaps make the error clearer if the env passed in .babelrc is returning {} or null?

Thanks

Empieza revisando la configuración de ENV en .babelrc y la ruta que falla en babel-plugin-transform-define/lib/index.js. Reproduce el caso en el que ENV devuelve null o {}, incluyendo un archivo que solo use una expresión unaria como typeof; se considera terminado cuando el fallo indica que el valor de ENV no es válido en lugar de exponer el críptico TypeError.

Escrito por el modelo de indexación a partir del texto del issue.