Fix crash on exit

Fixes a crash on exit in ~AnalyzerManager, where
EditorManager::instance() might be already 0.

Change-Id: Ie1d5aa5590d2dd763f5cb8c7e0a8a5e593fd2af6
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

src/plugins/debugger/debuggerplugin.cpp

@@ -513,8 +513,6 @@ public:
 
     ~DebugMode()
     {
-        // Make sure the editor manager does not get deleted.
-        //EditorManager::instance()->setParent(0);
         delete m_widget;
     }
 };