title: CollectionType expected argument of type "string or null", "array" given at property path "cc"
body: <p>Can someone explain why i am getting this error? I am using <code>CollectionType</code> for first time. Used <a href="https://symfony.com/doc/current/reference/forms/types/collection.html" rel="nofollow noreferrer">documentation</a>.
  Here is my part of where i am trying to use <code>CollectionType</code>:</p>
  
  <pre><code>$builder-&gt;add('cc', CollectionType::class, [
           'required' =&gt; false,
           'entry_type' =&gt; EmailType::class
  ])
  </code></pre>
  
  <p>and here is my request:</p>
  
  <pre><code>{
      "email" =&gt; "test@test.com",
      "description" =&gt; "test description",
      "subject" =&gt; "test",
      "cc" =&gt; array:1 [
           0 =&gt; "test1@test.com"
      ]
  }
  </code></pre>