Using `react-refresh/babel` 0.4.0 is giving me this error on a large number of files:

```
ERROR in ../orbit-app/src/hooks/useStores.ts
Module build failed (from ../node_modules/babel-loader/lib/index.js):
TypeError: Cannot read property '0' of undefined
    at Function.get (/Users/nw/projects/motion/orbit/node_modules/@babel/traverse/lib/path/index.js:115:33)
    at NodePath.unshiftContainer (/Users/nw/projects/motion/orbit/node_modules/@babel/traverse/lib/path/modification.js:191:31)
    at PluginPass.exit (/Users/nw/projects/motion/orbit/node_modules/react-refresh/cjs/react-refresh-babel.development.js:546:28)
```

I narrowed down that file to the simplest thing that causes it:

```
import { useContext } from 'react'

export default () => useContext()
```

_Originally posted by @natew in https://github.com/facebook/react/issues/16604#issuecomment-528708174_
}
          seenForSignature.add(node);
          
          const sigCallID = path.scope.generateUidIdentifier('_s');
          path.scope.parent.push({
            id: sigCallID,
            init: t.callExpression(t.identifier('$RefreshSig$'), []),
          });
          
          
          path
            .get('body')
            .unshiftContainer(
              'body',
              t.expressionStatement(t.callExpression(sigCallID, [])),
            );
          
          
          if (path.parent.type === 'VariableDeclarator') {
            let insertAfterPath = null;
            path.find(p => {
              if (p.parentPath.isBlock()) {
                insertAfterPath = p;
                return true;
              }
            });
            if (insertAfterPath === null) {
              return;
            }