Autoindex: return NGX_ERROR on error if headers were sent.

This prevents ngx_http_finalize_request() from issuing
ngx_http_special_response_handler() on a freed context.

src/http/modules/ngx_http_autoindex_module.c

diff --git a/src/http/modules/ngx_http_autoindex_module.c b/src/http/modules/ngx_http_autoindex_module.c
index e3dcfd0..e21d8d7 100644
--- a/src/http/modules/ngx_http_autoindex_module.c
+++ b/src/http/modules/ngx_http_autoindex_module.c
@@ -388,7 +388,7 @@
 
     b = ngx_create_temp_buf(r->pool, len);
     if (b == NULL) {
-        return NGX_HTTP_INTERNAL_SERVER_ERROR;
+        return NGX_ERROR;
     }
 
     if (entries.nelts > 1) {
@@ -649,7 +649,7 @@
                       ngx_close_dir_n " \"%V\" failed", name);
     }
 
-    return NGX_HTTP_INTERNAL_SERVER_ERROR;
+    return r->header_sent ? NGX_ERROR : NGX_HTTP_INTERNAL_SERVER_ERROR;
 }