Cleaned up the cleanup process.

Author: gunterkoenigsmann

src/Worksheet.cpp

@@ -327,14 +327,11 @@ Worksheet::~Worksheet()
 
   m_mainToolBar = NULL;
 
-  if (m_tree != NULL)
-    DestroyTree();
-  m_tree = NULL;
-
+  ClearDocument();
+  
   wxDELETE(m_configuration);
-  wxDELETE(m_dc);
-  m_dc = NULL;
   m_configuration = NULL;
+  m_dc = NULL;
 }
 
 /***

src/wxMaximaFrame.cpp

@@ -257,10 +257,13 @@ wxMaximaFrame::~wxMaximaFrame()
   // We cannot call delete here as we don't know if there are still timer-
   // or similar events pending for the wxWindows we want to free the memory
   // for.
-  m_history->Destroy();
-  m_worksheet->m_tableOfContents->Destroy();
-  m_worksheet->m_tableOfContents = NULL;
-  m_worksheet->Destroy();
+  //
+  // And as their parent is destroyed all objects in the frame will
+  // automatically be destroyed, anyway.
+  // m_history->Destroy();
+  // m_worksheet->m_tableOfContents->Destroy();
+  // m_worksheet->m_tableOfContents = NULL;
+  // m_worksheet->Destroy();
 }
 
 void wxMaximaFrame::set_properties()