use content type of the parent request in SSI stub block output
instead of default one

src/http/modules/ngx_http_ssi_filter_module.c

diff --git a/src/http/modules/ngx_http_ssi_filter_module.c b/src/http/modules/ngx_http_ssi_filter_module.c
index 2520cdb..d95b297 100644
--- a/src/http/modules/ngx_http_ssi_filter_module.c
+++ b/src/http/modules/ngx_http_ssi_filter_module.c
@@ -2061,9 +2061,9 @@
     out = data;
 
     if (!r->header_sent) {
-        if (ngx_http_set_content_type(r) != NGX_OK) {
-            return NGX_ERROR;
-        }
+        r->headers_out.content_type_len =
+                                      r->parent->headers_out.content_type_len;
+        r->headers_out.content_type = r->parent->headers_out.content_type;
 
         if (ngx_http_send_header(r) == NGX_ERROR) {
             return NGX_ERROR;