Fix guarding for event id in showReportDialog docs (#8925)

Author: Luca Forstner

src/platform-includes/user-feedback/example-widget/javascript.electron.mdx

@@ -8,8 +8,8 @@ init({
   beforeSend(event) {
     // Check if it is an exception, if so, show the report dialog
     // Note that this only will work in the renderer process, it's a noop on the main process
-    if (event.exception) {
-      showReportDialog();
+    if (event.exception && event.event_id) {
+      showReportDialog({ eventId: event_id });
     }
     return event;
   },

src/platform-includes/user-feedback/example-widget/javascript.mdx

@@ -8,7 +8,7 @@ If you're using a framework like [React](/platforms/javascript/guides/react/) or
     dsn: "___PUBLIC_DSN___",
     beforeSend(event, hint) {
       // Check if it is an exception, and if so, show the report dialog
-      if (event.exception) {
+      if (event.exception && event.event_id) {
         Sentry.showReportDialog({ eventId: event.event_id });
       }
       return event;