drop unused PaneManagerDying enumerator

Change-Id: I4b17d19b5f1f84df38cbb5372ca2d0b425f22698

sd/source/ui/inc/EventMultiplexer.hxx

@@ -71,10 +71,6 @@ enum class EventMultiplexerEventId
     */
     ViewAdded,
 
-    /** The PaneManager is being destroyed.
-    */
-    PaneManagerDying,
-
     /** Edit mode was (or is being) switched to normal mode.  Find
         EventId::EditModeMaster below.
     */

sd/source/ui/view/ToolBarManager.cxx

@@ -870,10 +870,6 @@ IMPL_LINK(ToolBarManager::Implementation,EventMultiplexerCallback,
             SetValid(false);
             break;
 
-        case EventMultiplexerEventId::PaneManagerDying:
-            SetValid(false);
-            break;
-
         default: break;
     }
 }