fix 185176, don't hold open .msf files for newly discovered imap folders, r/sr=mscott

git-svn-id: svn://10.0.0.236/trunk@144911 18797224-902f-48f8-a5cc-f745e15eee43

mozilla/mailnews/imap/src/nsImapIncomingServer.cpp

@@ -1338,6 +1338,8 @@ NS_IMETHODIMP nsImapIncomingServer::PossibleImapMailbox(const char *folderPath,
       }
     }
   }
+  if (!found && child)
+    child->SetMsgDatabase(nsnull); // close the db, so we don't hold open all the .msf files for new folders
   return NS_OK;
 }