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/os2/treectrl.cpp

@@ -80,11 +80,7 @@ public:
     wxTreeItemInternalData() {}
     ~wxTreeItemInternalData()
     {
-        if(m_pAttr)
-        {
-            delete m_pAttr;
-            m_pAttr = NULL;
-        }
+        wxDELETE(m_pAttr);
     }
 
     wxTreeItemAttr*                 m_pAttr;