Fix hydration with empty spread attributes (#4647)

* Fix hydration of empty spread attributes

* add a regression test

* fix doctest

packages/playwright-tests/fullstack-spread.spec.js

@@ -0,0 +1,13 @@
+// @ts-check
+const { test, expect } = require("@playwright/test");
+
+test("spread attributes hydrate", async ({ page }) => {
+  await page.goto("http://localhost:7979");
+
+  // Expect the page to contain the button
+  const counter = page.locator("#counter");
+  await expect(counter).toHaveText("Count: 0");
+  // Clicking on the button should increment the count
+  await counter.click();
+  await expect(counter).toHaveText("Count: 1");
+});