placeholder (null or "") doesn't work with textarea

[Der-K-2000]

Even though I put a "placeholder" in the textarea's option it will be ignored in the formular in the backend.

This

{
  "placeholder": null
}

and

{
  "placeholder": ""
}

lead to the output: Text...

Only

{
  "placeholder": " "
}

works correctly (so with an additional Space).