Fixed a bug with React Native plugins loading

Summary:
Fixed bug with "Hermes Debugger" and "React Dev Tools" plugin loading reported on GitHub: https://github.com/facebook/flipper/issues/2545.

Changelog: Fixed bug with React Native plugins not loaded: Hermes Debugger, React Dev Tools etc.

Reviewed By: mweststrate

Differential Revision: D29516394

fbshipit-source-id: 4620e3d2b49ca2a1d3a5b2dd76d40d4667a0980b

desktop/app/src/selectors/connections.tsx

@@ -36,9 +36,9 @@ export const getActiveClient = createSelector(
 
 export const getMetroDevice = createSelector(getDevices, (devices) => {
   return (
-    (devices.find(
-      (device) => device.os === 'Metro' && !device.isArchived,
-    ) as MetroDevice) ?? null
+    (devices.find((device) => device.os === 'Metro' && !device.isArchived) as
+      | MetroDevice
+      | undefined) ?? null
   );
 });