[gnome-builder/gnome-builder-3-26] html-preview: fix invalid use of view

[Christian Hergert <chergert src gnome org>]

commit e0c6122a364afdf26075c25901ef09e0f0885717
Author: Christian Hergert <chergert redhat com>
Date:   Thu Sep 21 01:36:02 2017 -0700

    html-preview: fix invalid use of view

 .../html-preview/html_preview_plugin/__init__.py   |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/plugins/html-preview/html_preview_plugin/__init__.py 
b/plugins/html-preview/html_preview_plugin/__init__.py
index 3f1a320..f250b72 100644
--- a/plugins/html-preview/html_preview_plugin/__init__.py
+++ b/plugins/html-preview/html_preview_plugin/__init__.py
@@ -256,7 +256,8 @@ class HtmlPreviewAddin(GObject.Object, Ide.EditorViewAddin):
     def preview_activated(self, *args):
         global can_preview_rst
 
-        if self.view is None:
+        view = self.view
+        if view is None:
             return
 
         if self.lang_id == 'rst':