[material-ui][SwipeableDrawer] Safe access of ref value in SwipeableDrawer

[shapeinabox]

• I have followed (at least) the PR section of the contributing guide.

In the company I work for we're using MUI as the base for the designs system, and we started receiving a Sentry issue affecting a non-trivial amount of users. Mostly happening on our capacitor app on iOS devices.

After some investigation, it seems clear the error is surfacing from the mui code. Here's a screenshot of the minified code from the capacitor bundled file that Sentry mentioned.

Looking in the material-ui codebase for a similar line of code that could cause the issue, I stumbled upon the SwipeableDrawer, where I found a condition that looks really similar to the minified code that's throwing the error. Indeed, it looks like the ref is not accessed safely in the if condition.

This simple fix I'm submitting here should solve the issue.

[mnajdova]

Can you please create a reproduction. I can't think of scenarios where these refs won't be already defined. Have you investigated what may be causing this?