[gnome-builder] xml-pack: fix the DTD not-validated error message

[Sébastien Lafargue <slafargue src gnome org>]

commit 3c0db11dded3b889bffb09e2081b9df3c92f71f6
Author: Sebastien Lafargue <slafargue gnome org>
Date:   Wed Jul 19 00:38:47 2017 +0200

    xml-pack: fix the DTD not-validated error message

 plugins/xml-pack/ide-xml-tree-builder.c |   10 ++++++++--
 1 files changed, 8 insertions(+), 2 deletions(-)
---
diff --git a/plugins/xml-pack/ide-xml-tree-builder.c b/plugins/xml-pack/ide-xml-tree-builder.c
index 99ea34d..5c12343 100644
--- a/plugins/xml-pack/ide-xml-tree-builder.c
+++ b/plugins/xml-pack/ide-xml-tree-builder.c
@@ -351,8 +351,14 @@ ide_xml_tree_builder_build_tree_cb2 (GObject      *object,
 
           if (!ide_xml_validator_validate (self->validator, doc, &diagnostics))
             {
-              uri = g_file_get_uri (entry->file);
-              msg = g_strdup_printf ("Can't validate the schema: '%s'", uri);
+              if (entry->file == NULL)
+                msg = g_strdup_printf ("Can't validate the internal schema");
+              else
+                {
+                  uri = g_file_get_uri (entry->file);
+                  msg = g_strdup_printf ("Can't validate the schema: '%s'", uri);
+                }
+
               diagnostic = create_diagnostic (context,
                                               msg,
                                               state->file,