title: Updating to Nuxt3 RC3 produces client side errors
body: <p>I am out of options to ask for help. I used an older version of nuxt3 and after upgrading to <code>3.0.0-3c.3</code>, starting the project with <code>nuxt dev</code> results in a broken site, giving me a cryptic error message that I have no idea how to debug:</p>
  <pre><code>Error while mounting app: TypeError: Cannot read properties of undefined (reading 'modules')
      at _sfc_main.setup (root.vue:17:16)
      at callWithErrorHandling (runtime-core.esm-bundler.js:155:22)
      at setupStatefulComponent (runtime-core.esm-bundler.js:7109:29)
      at setupComponent (runtime-core.esm-bundler.js:7064:11)
      at mountComponent (runtime-core.esm-bundler.js:4951:13)
      at hydrateNode (runtime-core.esm-bundler.js:4153:21)
      at hydrate2 (runtime-core.esm-bundler.js:4068:9)
      at mount (runtime-core.esm-bundler.js:3900:25)
      at Object.app.mount (runtime-dom.esm-bundler.js:1612:20)
      at initApp (entry.mjs:34:12)
  (anonymous) @ entry.mjs:39
  </code></pre>
  <p>I have no idea how to fix this - I am entirely blocked and I am writing here as a last resort. Any ideas on how to fix it?</p>