If you pass invalid input to a function such as soup_header_parse_param_list_strict()
it can cause an overflow if it decodes the input to UTF-8.

This should never happen with valid UTF-8 input which libsoup's client API
ensures, however it's server API does not currently.

Otherwise we can enter in a read loop because we were not
validating the data until the all the data was read.

Fixes #391

Otherwise the server will have already sent a few more wrong
bytes and the client will continue getting errors to copy
but the error is already != NULL and it will assert

It is passed to the function as `int` in all uses in the codebase (as a literal or as a `gint` result of `g_uri_get_port`).

This is the same change as commit 29b96fab "websocket-test: disconnect
error copy after the test ends", and is done for the same reason, but
replicating it into a different function.

Fixes: 6adc0e3e "websocket: process the frame as soon as we read data"
Resolves: https://gitlab.gnome.org/GNOME/libsoup/-/issues/399


Signed-off-by: Simon McVittie <smcv@debian.org>

Co-Author: Ar Jun <pkillarjun@protonmail.com>