svgz failed to open by rsvg-convert because to MIME registered with svgz (only svg)

I suggest something like

@@ -227,12 +246,17 @@
                                                 NULL,
                                                 NULL))) {
                 const char *content_type;
-                char *gz_content_type;
-
                 content_type = g_file_info_get_content_type (file_info);
+#ifdef G_OS_WIN32
+/* Seems win32 don't have svgz mime registry, just verify the extension */
+                if (!stricmp (content_type, ".svgz"))
+                    compressed = TRUE;
+#else
+                char *gz_content_type;
                 gz_content_type = g_content_type_from_mime_type ("application/x-gzip");
                 compressed = (content_type != NULL && g_content_type_is_a (content_type, gz_content_type));
                 g_free (gz_content_type);
+#endif
                 g_object_unref (file_info);
             }