fix for crasher on exit. close the dbview when the mailnews xul is unloaded.

when the db goes away (on shutdown) we won't get notified, so we won't poke the
outliner, which is already gone.  sr=bienvenu

mailnews/base/resources/content/mailWindow.js

@@ -64,6 +64,11 @@ var gIsEditableMsgFolder = false;
 
 function OnMailWindowUnload()
 {
+  var dbview = GetDBView();
+  if (dbview) {
+    dbview.close(); 
+  }
+
   var mailSession = Components.classes[mailSessionContractID].getService();
   if(mailSession)
   {

mailnews/base/src/nsMsgThreadedDBView.cpp

@@ -49,7 +49,7 @@ NS_IMETHODIMP nsMsgThreadedDBView::Open(nsIMsgFolder *folder, nsMsgViewSortTypeV
 
 NS_IMETHODIMP nsMsgThreadedDBView::Close()
 {
-    return NS_ERROR_NOT_IMPLEMENTED;
+  return nsMsgDBView::Close();
 }
 
 nsresult nsMsgThreadedDBView::InitThreadedView(PRInt32 *pCount)