[sushi] mainWindow: fix uninitialized variable

[Cosimo Cecchi <cosimoc src gnome org>]

commit c254e6b54c91f7f8ba54440e8ab437e6a62ad32f
Author: Cosimo Cecchi <cosimoc gnome org>
Date:   Sat Feb 11 15:17:10 2017 -0800

    mainWindow: fix uninitialized variable

 src/js/ui/mainWindow.js |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/src/js/ui/mainWindow.js b/src/js/ui/mainWindow.js
index 48ad33d..f4a5108 100644
--- a/src/js/ui/mainWindow.js
+++ b/src/js/ui/mainWindow.js
@@ -51,6 +51,7 @@ const MainWindow = new Lang.Class({
         args = args || {};
 
         this._background = null;
+        this._isFullScreen = false;
         this._pendingRenderer = null;
         this._renderer = null;
         this._texture = null;