[glom] BusyCursor: Correct a wrong null check.

[Murray Cumming <murrayc src gnome org>]

commit c827f1c3fc7265b287e251dd2ad4ccdca7bae131
Author: Murray Cumming <murrayc murrayc com>
Date:   Wed Feb 10 21:18:39 2016 +0100

    BusyCursor: Correct a wrong null check.
    
    I guess this is why I haven't been seeing the busy cursor recently.
    Found by clang-tidy.

 glom/bakery/busy_cursor.cc |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/glom/bakery/busy_cursor.cc b/glom/bakery/busy_cursor.cc
index 116095a..ffdf244 100644
--- a/glom/bakery/busy_cursor.cc
+++ b/glom/bakery/busy_cursor.cc
@@ -16,7 +16,7 @@ BusyCursor::BusyCursor(Gtk::Window& window, Gdk::CursorType cursor_type)
 BusyCursor::BusyCursor(Gtk::Window* window, Gdk::CursorType cursor_type)
 : m_pWindow(window) //If this is a nested cursor then remember the previously-set cursor, so we can restore 
it.
 {
-  if(m_pWindow)
+  if(!m_pWindow)
     return;
 
   m_Cursor = Gdk::Cursor::create(m_pWindow->get_display(), cursor_type);