fix 298479, rename local folder to name of just deleted virtual folder loses data, sr=mscott, a=chofmann

mailnews/base/src/nsMsgAccountManager.cpp

@@ -3113,7 +3113,8 @@ NS_IMETHODIMP nsMsgAccountManager::OnItemRemoved(nsIRDFResource *parentItem, nsI
   folder->GetFlags(&folderFlags);
   if (folderFlags & MSG_FOLDER_FLAG_VIRTUAL) // if we removed a VF, flush VF list to disk.
     rv = SaveVirtualFolders();
-
+  // clear flags on deleted folder, especially MSG_FOLDER_FLAG_VIRTUAL
+  folder->SetFlags(0);
   // need to check if the underlying folder for a VF was removed, in which case we need to
   // remove the virtual folder.