이 오류 왜뜨는 걸까요?

[khw0705]

TypeError: Error #1009: null 객체 참조의 속성이나 메서드에 액세스할 수 없습니다.
at net.daum.mclient::TweetieService/::command()
at net.daum.mclient::TweetieService/setenv()
at net.daum.mclient.client::TweetieClient/setenv()
at net.daum.cafe.chat.client.views::UserListPanel/changeTypingInfo()
at flash.events::EventDispatcher/flash.events:EventDispatcher::dispatchEventFunction()
at flash.events::EventDispatcher/dispatchEvent()
at net.daum.cafe.chat.client.event::ChatEventDispatcher/changeTypingInfo()
at net.daum.cafe.chat.client.manager::ExternalFunctionManager/changeTypingInfo()
at Function/http://adobe.com/AS3/2006/builtin::apply()

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다음 채팅방 들어가니까 이런 오류가 뜨고 안되네요