don't use annoying and unneeded in C++ casts of NULL to "T *" in all other files neither

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@58227 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/univ/winuniv.cpp

@@ -129,7 +129,7 @@ void wxWindow::Init()
 {
 #if wxUSE_SCROLLBAR
     m_scrollbarVert =
-    m_scrollbarHorz = (wxScrollBar *)NULL;
+    m_scrollbarHorz = NULL;
 #endif // wxUSE_SCROLLBAR
 
     m_isCurrent = false;