Avoid resetting the background color when clearing out blank areas, as
it may have been set to something other than COLOR_WINDOW by the
application.

controls/listbox.c

diff --git a/controls/listbox.c b/controls/listbox.c
index 4f489cb..5f9f281 100644
--- a/controls/listbox.c
+++ b/controls/listbox.c
@@ -988,7 +988,6 @@
             if (!IS_OWNERDRAW(descr))
             {
                 /* Clear the bottom of the column */
-                SetBkColor( hdc, GetSysColor( COLOR_WINDOW ) );
                 if (rect.top < descr->height)
                 {
                     rect.bottom = descr->height;
@@ -1018,7 +1017,6 @@
     if (!IS_OWNERDRAW(descr))
     {
         /* Clear the remainder of the client area */
-        SetBkColor( hdc, GetSysColor( COLOR_WINDOW ) );
         if (rect.top < descr->height)
         {
             rect.bottom = descr->height;