mobx-react observer broken react-hot-loader

### Description

mobx-react observer broken react-hot-loader

### Expected behavior

hot reload success

### Actual behavior

hot reload broken

### Environment

React Hot Loader version: react-hot-loader@4.12.13

Run these commands in the project folder and fill in their results:

1. `node -v`: v11.14.0
2. `npm -v`: 6.13.7

### Reproducible Demo
demo: https://github.com/gaearon/react-hot-loader/pull/1418/files
pull this github mr and edit examples/typescript/src/Counter.tsx:32
react-hot-loader will not work

ref: https://github.com/mobxjs/mobx-react/issues/833