[gtkmm] gtk-demo/demowindow: Remove unnecessary null check

[Daniel Boles <dboles src gnome org>]

commit ba404c1e5b754101725e0fcace6218cd31066a4f
Author: Daniel Boles <dboles src gnome org>
Date:   Fri May 26 20:15:29 2017 +0100

    gtk-demo/demowindow: Remove unnecessary null check
    
    There is no way that the pointer d can become null here.

 demos/gtk-demo/demowindow.cc |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/demos/gtk-demo/demowindow.cc b/demos/gtk-demo/demowindow.cc
index a76ad51..5a7a057 100644
--- a/demos/gtk-demo/demowindow.cc
+++ b/demos/gtk-demo/demowindow.cc
@@ -123,7 +123,7 @@ void DemoWindow::fill_tree()
   /* this code only supports 1 level of children. If we
    * want more we probably have to use a recursing function.
    */
-  for (auto d = testgtk_demos; d && d->title; ++d)
+  for (auto d = testgtk_demos; d->title; ++d)
   {
     auto row = *(m_refTreeStore->append());