[gnome-builder] html-preview: fix use from callback

[Christian Hergert <chergert src gnome org>]

commit 6ec10f9e31d06225bc01529a89c9da228ae3a4f1
Author: Christian Hergert <chergert redhat com>
Date:   Thu Sep 21 01:31:39 2017 -0700

    html-preview: fix use from callback

 src/plugins/html-preview/html_preview.py |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/plugins/html-preview/html_preview.py b/src/plugins/html-preview/html_preview.py
index 36f95c4..59f5c51 100644
--- a/src/plugins/html-preview/html_preview.py
+++ b/src/plugins/html-preview/html_preview.py
@@ -253,7 +253,7 @@ class HtmlPreviewAddin(GObject.Object, Ide.EditorViewAddin):
 
         return sphinx_builddir
 
-    def preview_activated(self):
+    def preview_activated(self, *args):
         global can_preview_rst
 
         if self.view is None: