[Bug] Doesn't work for `::placeholder { }`

[wenfangdu]

::placeholder {
} /* 👈 put cursor on }, and use ds{ */

{} won't get removed.

[wenfangdu]

A workaround is to use da{.

[idbrii]

It's not because of placeholder. Surround won't remove because the {} aren't surrounding anything. If there was any text (even non-newline whitespace) between them, ds{ would work.

[idbrii]

Related to #275: Looks like empty braces are generally not handled?