refinement doesn't run type checks in production

Bug report

• I've checked documentation and searched for existing issues
• I've made sure my project is based on the latest MST version
• Fork this code sandbox or another minimal reproduction.

Sandbox link or minimal reproduction code

1. Open: https://codesandbox.io/s/mst-refinement-dev-mode-xk0w34?file=/.env
2. Press 'Add' button

Describe the expected behavior

Crash with unhandled exception:

[mobx-state-tree] Error while converting `{"title":""}` to `Todo`:

because I modified Todo.js to be:

types.refinement(types.string, (str) => str.length > 0),

Describe the observed behavior

It doesn't crash.

Note that if you delete the .env file I added (putting it back in to development mode) the exception is raised.