Fix Date Label In Crashes Plugin

Summary: The date type for crash reports was updated in D29327501 (aff02b2ca1) from `Date` to `number`. Unset values were previously `null` but became `NaN` in this change. `NaN` is nonnull so the backup value of `Date.now()` was not getting triggered properly and leading to "Invalid Date" to show up in the UI.

Reviewed By: passy

Differential Revision: D31702757

fbshipit-source-id: da93b1f79eb633b2f49dcffbe680d56d47a23ea0

desktop/plugins/public/crash_reporter/index.tsx

@@ -47,7 +47,7 @@ export function devicePlugin(client: DevicePluginClient) {
       callstack: payload.callstack,
       name: payload.name,
       reason: payload.reason,
-      date: payload.date ?? Date.now(),
+      date: payload.date || Date.now(),
     };
 
     crashes.update((draft) => {