set "Content-Length: 0" for errors handled by "return 204"

src/http/ngx_http_request.h

diff --git a/src/http/ngx_http_request.h b/src/http/ngx_http_request.h
index b9ad2b5..08ccd13 100644
--- a/src/http/ngx_http_request.h
+++ b/src/http/ngx_http_request.h
@@ -430,6 +430,7 @@
     unsigned                          plain_http:1;
     unsigned                          chunked:1;
     unsigned                          header_only:1;
+    unsigned                          zero_body:1;
     unsigned                          keepalive:1;
     unsigned                          lingering_close:1;
     unsigned                          discard_body:1;

src/http/ngx_http_script.c

diff --git a/src/http/ngx_http_script.c b/src/http/ngx_http_script.c
index 3a9e2a8..e8bce19 100644
--- a/src/http/ngx_http_script.c
+++ b/src/http/ngx_http_script.c
@@ -841,6 +841,7 @@
 
     if (code->status == NGX_HTTP_NO_CONTENT) {
         e->request->header_only = 1;
+        e->request->zero_body = 1;
     }
 
     e->ip += sizeof(ngx_http_script_return_code_t) - sizeof(uintptr_t);

src/http/ngx_http_special_response.c

diff --git a/src/http/ngx_http_special_response.c b/src/http/ngx_http_special_response.c
index d249c27..c8190ed 100644
--- a/src/http/ngx_http_special_response.c
+++ b/src/http/ngx_http_special_response.c
@@ -455,25 +455,32 @@
 
     msie_padding = 0;
 
-    if (error_pages[err].len) {
-        r->headers_out.content_length_n = error_pages[err].len
-                                          + sizeof(error_tail) - 1;
+    if (!r->zero_body) {
+        if (error_pages[err].len) {
+            r->headers_out.content_length_n = error_pages[err].len
+                                              + sizeof(error_tail) - 1;
 
-        if (clcf->msie_padding
-            && r->headers_in.msie
-            && r->http_version >= NGX_HTTP_VERSION_10
-            && error >= NGX_HTTP_BAD_REQUEST
-            && error != NGX_HTTP_REQUEST_URI_TOO_LARGE)
-        {
-            r->headers_out.content_length_n += sizeof(ngx_http_msie_stub) - 1;
-            msie_padding = 1;
+            if (clcf->msie_padding
+                && r->headers_in.msie
+                && r->http_version >= NGX_HTTP_VERSION_10
+                && error >= NGX_HTTP_BAD_REQUEST
+                && error != NGX_HTTP_REQUEST_URI_TOO_LARGE)
+            {
+                r->headers_out.content_length_n +=
+                                                sizeof(ngx_http_msie_stub) - 1;
+                msie_padding = 1;
+            }
+
+            r->headers_out.content_type.len = sizeof("text/html") - 1;
+            r->headers_out.content_type.data = (u_char *) "text/html";
+
+        } else {
+            r->headers_out.content_length_n = -1;
         }
 
-        r->headers_out.content_type.len = sizeof("text/html") - 1;
-        r->headers_out.content_type.data = (u_char *) "text/html";
-
     } else {
-        r->headers_out.content_length_n = -1;
+        r->headers_out.content_length_n = 0;
+        err = 0;
     }
 
     if (r->headers_out.content_length) {