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/generic/grid.cpp

@@ -2100,8 +2100,7 @@ wxGrid::SetTable(wxGridTableBase *table,
             m_table = NULL;
         }
 
-        delete m_selection;
-        m_selection = NULL;
+        wxDELETE(m_selection);
 
         m_ownTable = false;
         m_numRows = 0;