[SahinurDEV]

Problem

Sender.sendFrame() writes an unmasked frame as two socket writes (header, then payload) even when the payload is empty. On Electron on some arm64 Linux kernels with a 39-bit address space, net.Socket#write() of a zero-length Buffer fails with EFAULT and destroys the socket. That kills empty server-side ping/pong/message/close() frames (including the automatic pong to an empty client ping) with close code 1006.

Cause

if (list.length === 2) {
  this._socket.write(list[0]);
  this._socket.write(list[1], cb); // zero-length Buffer for empty frames
}

Fix

Skip the payload write when it is empty:

if (list.length === 2 && list[1].length !== 0) {

The frame header already encodes length 0, so the bytes on the wire are unchanged. Masked empty frames are unaffected (they are already a single write).

Tests

Added unit tests that assert an empty unmasked ping is a single write of the header, and a non-empty unmasked ping still uses two writes. Full test/sender.test.js passes; suite otherwise green aside from an unrelated EADDRINUSE flake on port 1337 in this environment.

Fixes #2339