[pitivi] mediafilepreviewer: Make sure to show the video previewer

[Thibault Saunier <tsaunier src gnome org>]

commit a97c7453435346c0921af63ab44b000909c745c3
Author: Thibault Saunier <tsaunier gnome org>
Date:   Thu Jul 2 11:31:02 2015 +0200

    mediafilepreviewer: Make sure to show the video previewer
    
    Summary: Depends on D268
    
    Reviewers: Mathieu_Du, aleb
    
    Differential Revision: https://phabricator.freedesktop.org/D269

 pitivi/mediafilespreviewer.py |    1 +
 pitivi/viewer.py              |    3 +++
 2 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/pitivi/mediafilespreviewer.py b/pitivi/mediafilespreviewer.py
index f2d5e06..f64b044 100644
--- a/pitivi/mediafilespreviewer.py
+++ b/pitivi/mediafilespreviewer.py
@@ -111,6 +111,7 @@ class PreviewWidget(Gtk.Grid, Loggable):
         self.preview_video = ViewerWidget(self.player.video_sink)
         self.preview_video.props.hexpand = minimal
         self.preview_video.props.vexpand = minimal
+        self.preview_video.show_all()
         self.attach(self.preview_video, 0, 0, 1, 1)
 
         # An image for images and audio
diff --git a/pitivi/viewer.py b/pitivi/viewer.py
index ed02a74..a41c86c 100644
--- a/pitivi/viewer.py
+++ b/pitivi/viewer.py
@@ -489,6 +489,9 @@ class TransformationBox(Gtk.EventBox, Loggable):
         self.add_events(Gdk.EventMask.SCROLL_MASK)
 
     def __setupEditSource(self):
+        if not self.app:
+            return
+
         if self.__editSource:
             return
         elif self.app.project_manager.current_project.pipeline.getState() != Gst.State.PAUSED: