Error: Meteor code must always run within a Fiber

I get this error when I use `Meteor.user()` inside `withTracker` functions, **only on server**.

```
Error running template: Error: Meteor code must always run within a Fiber. Try wrapping callbacks that you pass to non-Meteor libraries with Meteor.bindEnvironment.
```
It happens at this line in the `react-meteor-data` package: https://github.com/meteor/react-packages/blob/796a075a4bbb36212e6a74c9f3576b119d31c474/packages/react-meteor-data/ReactMeteorData.jsx#L34

Meteor.bindEnvironment can't be used because it eats up the return values.

Any ideas for solving this?

Start at packages/react-meteor-data/ReactMeteorData.jsx line 34 and reproduce the server-side withTracker call that uses Meteor.user(). Investigate how the Fiber error arises and whether the existing Meteor.bindEnvironment behavior affects return values; done means the server case runs without the Fiber error while preserving the expected return value.

Written by the indexing model from the issue text.