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_
const fnNode = fnScope.block;
      if (!hookCalls.has(fnNode)) {
        hookCalls.set(fnNode, []);
      }
      let hookCallsForFn = hookCalls.get(fnNode);
      let key = '';
      if (path.parent.type === 'VariableDeclarator') {
        
        key = path.parentPath.get('id').getSource();
      }
      
      const args = path.get('arguments');
      if (name === 'useState' && args.length > 0) {
        
        key += '(' + args[0].getSource() + ')';
      } else if (name === 'useReducer' && args.length > 1) {
        
        key += '(' + args[1].getSource() + ')';
      }
      hookCallsForFn.push({
        callee: path.node.callee,
        name,
        key,
      });
    },
  };
  return {
    visitor: {
      ExportDefaultDeclaration(path) {