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/osx/core/bitmap.cpp

@@ -1384,7 +1384,7 @@ int wxBitmap::GetDepth() const
 
 wxMask *wxBitmap::GetMask() const
 {
-   wxCHECK_MSG( Ok(), (wxMask *) NULL, wxT("invalid bitmap") );
+   wxCHECK_MSG( Ok(), NULL, wxT("invalid bitmap") );
 
    return M_BITMAPDATA->m_bitmapMask;
 }