10.10のスクリプトエディタで、アプリで保存、ハンドラ実行後に終了しない

use framework "AppKit"
on didMount:aNotification
set volName to aNotification's userInfo's |NSWorkspaceVolumeLocalizedNameKey|
using terms from scripting additions
display notification (volName as Unicode text) & " がマウントされたよ"
end using terms from
end didMount:
tell current application
tell my NSWorkspace's sharedWorkspace()'s notificationCenter() to addObserver:me selector:"didMount:" |name|:"NSWorkspaceDidMountNotification" object:(missing value)
end tell