[gnome-builder/gnome-builder-3-28] xml-pack: don't look for a DTD with html5 docs

[Sébastien Lafargue <slafargue src gnome org>]

commit d59748c3805f4f462fe0692c3257d6c9807c2cfb
Author: Sebastien Lafargue <slafargue gnome org>
Date:   Mon Apr 23 20:08:06 2018 +0200

    xml-pack: don't look for a DTD with html5 docs

 src/plugins/xml-pack/ide-xml-parser.c | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/src/plugins/xml-pack/ide-xml-parser.c b/src/plugins/xml-pack/ide-xml-parser.c
index d7996b21c..dfb1bde35 100644
--- a/src/plugins/xml-pack/ide-xml-parser.c
+++ b/src/plugins/xml-pack/ide-xml-parser.c
@@ -431,6 +431,9 @@ ide_xml_parser_internal_subset_sax_cb (ParserState   *state,
   g_assert (state != NULL);
   g_assert (IDE_IS_XML_PARSER (state->self));
 
+  if (dzl_str_empty0 ((gchar *)external_id) || dzl_str_empty0 ((gchar *)system_id))
+    return;
+
   entry = ide_xml_schema_cache_entry_new ();
   entry->kind = SCHEMA_KIND_DTD;
   ide_xml_sax_get_location (state->sax_parser, &entry->line, &entry->col, NULL, NULL, NULL, NULL);