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/stc/stctest.cpp

@@ -682,17 +682,13 @@ AppAbout::AppAbout (wxWindow *parent,
 }
 
 AppAbout::~AppAbout () {
-    if (m_timer)  {
-        delete m_timer;
-        m_timer = NULL;
-    }
+    wxDELETE(m_timer);
 }
 
 //----------------------------------------------------------------------------
 // event handlers
 void AppAbout::OnTimerEvent (wxTimerEvent &WXUNUSED(event)) {
-    if (m_timer) delete m_timer;
-    m_timer = NULL;
+    wxDELETE(m_timer);
     EndModal (wxID_OK);
 }