Use wxDELETE() and wxDELETEA() when possible.

Use wxDELETE[A]() functions which automatically NULL out their arguments after
deleting them instead of doing it manually.

Closes #9685.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@64656 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

samples/html/printing/printing.cpp

@@ -223,8 +223,7 @@ MyFrame::MyFrame(const wxString& title, const wxPoint& pos, const wxSize& size)
 // frame destructor
 MyFrame::~MyFrame()
 {
-    delete m_Prn;
-    m_Prn = (wxHtmlEasyPrinting *) NULL;
+    wxDELETE(m_Prn);
 }