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/html/helpfrm.cpp

@@ -81,7 +81,7 @@ void wxHtmlHelpFrame::Init(wxHtmlHelpData* data)
     // Simply pass the pointer on to the help window
     m_Data = data;
     m_HtmlHelpWin = NULL;
-    m_helpController = (wxHtmlHelpController*) NULL;
+    m_helpController = NULL;
 }
 
 void wxHtmlHelpFrame::SetController(wxHtmlHelpController* controller)