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

src/propgrid/manager.cpp

@@ -623,8 +623,7 @@ wxPropertyGridManager::~wxPropertyGridManager()
     END_MOUSE_CAPTURE
 
     //m_pPropGrid->ClearSelection();
-    delete m_pPropGrid;
-    m_pPropGrid = NULL;
+    wxDELETE(m_pPropGrid);
 
     size_t i;
     for ( i=0; i<m_arrPages.size(); i++ )