`NGX_ERROR` is dealt with twice in `ngx_http_echo_send_chain_link`

[duhoobo]

     99 ngx_int_t
    100 ngx_http_echo_send_chain_link(ngx_http_request_t* r,
    101     ngx_http_echo_ctx_t *ctx, ngx_chain_t *in)
    102 {
    103     ngx_int_t        rc;
    104       
    105     rc = ngx_http_echo_send_header_if_needed(r, ctx);
    106 
    107     if (rc == NGX_ERROR || rc > NGX_OK || r->header_only) {
    108         return rc;
    109     } 
    110     
    111     if (rc == NGX_ERROR) {
    112         return NGX_HTTP_INTERNAL_SERVER_ERROR;
    113     } 

[agentzh]

@duhoobo Fixed. Thanks!