fix crash running filter after the fact when a move/copy target folder is gone, sr=mscott 322283

mailnews/base/search/src/nsMsgFilterService.cpp

@@ -139,11 +139,15 @@ NS_IMETHODIMP nsMsgFilterService::CloseFilterList(nsIMsgFilterList *filterList)
 /* save without deleting */
 NS_IMETHODIMP	nsMsgFilterService::SaveFilterList(nsIMsgFilterList *filterList, nsIFileSpec *filterFile)
 {
-	nsresult ret = NS_OK;
+  NS_ENSURE_ARG_POINTER(filterFile);
+  NS_ENSURE_ARG_POINTER(filterList);
+
+  nsresult ret = NS_OK;
   nsCOMPtr <nsIFileSpec> tmpFiltersFile;
   nsCOMPtr <nsIFileSpec> realFiltersFile;
   nsCOMPtr <nsIFileSpec> parentDir;
 
+
   nsSpecialSystemDirectory tmpFile(nsSpecialSystemDirectory::OS_TemporaryDirectory);
   tmpFile += "tmprules.dat";