help request: When I use ext-plugin-post-resp plugin, an error ocuurs "404 page not found "

### Description

Hello,apisix team!

I used go-runner to write an ext-plugin rewrites the response, and then configured it on the route, using the ext-plugin-post-resp plugin.

I do nothing in this plugin,just record a log. like this

`
func (p *RsaEncrypt) ResponseFilter(conf interface{}, w pkgHTTP.Response) {
log.Infof("plugin rsa_encrypt response_filter")
}
`

this is my route config. my upstream nodes can be accessed，it`s ok

Then I make a curl request，return "404 page not found"
but,when I remove the configuration of ext-plugin-post-resp plugin in route config，curl return 200 OK！

when 404 retuen ，accesslog is

hope your answer, thanks.

### Environment

- APISIX version : 3.8
- Operating system : linux 3.10
- OpenResty / Nginx version: openresty/1.25.3.1
- etcd version, if relevant : 3.5.0
- APISIX Dashboard version, if relevant:
- Plugin runner version, for issues related to plugin runners: ext-plugin-post-resp
- LuaRocks version, for installation issues : 2.3.0

Start by reproducing the APISIX 3.8 route behavior with ext-plugin-post-resp enabled, comparing it with the same route without that plugin. Inspect the Go runner's ResponseFilter entry point and the response handling around it. Done means identifying why the otherwise unchanged response becomes 404 and documenting or fixing the cause.

Written by the indexing model from the issue text.