enhance(frontend): bootでonunhandledrejectionでrenderErrorする場合、PromiseRejectionEvent.reasonを渡すように (#16563)

packages/backend/src/server/web/boot.js

@@ -13,7 +13,7 @@
 	};
 	window.onunhandledrejection = (e) => {
 		console.error(e);
-		renderError('SOMETHING_HAPPENED_IN_PROMISE', e);
+		renderError('SOMETHING_HAPPENED_IN_PROMISE', e.reason || e);
 	};
 
 	let forceError = localStorage.getItem('forceError');