Sec-WebSocket-Version missing from response on handshake error

[nerg4l]

RFC 6455 states the following in Section 11.3.5. Sec-WebSocket-Version:

The |Sec-WebSocket-Version| header field is used in the WebSocket
opening handshake. It is sent from the client to the server to
indicate the protocol version of the connection. This enables
servers to correctly interpret the opening handshake and subsequent
data being sent from the data, and close the connection if the server
cannot interpret that data in a safe manner. The |Sec-WebSocket-
Version| header field is also sent from the server to the client on
WebSocket handshake error, when the version received from the client
does not match a version understood by the server. In such a case,
the header field includes the protocol version(s) supported by the
server.

[nhooyr]

Nice catch, will fix.