http2: consider 0-length non-end DATA frames an error

This is intended to mitigate CVE-2019-9518.

Backport-PR-URL: https://github.com/nodejs/node/pull/29124
PR-URL: https://github.com/nodejs/node/pull/29122


Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>