AJAX :: Accordion Extender + JS Error?

I used accordion control and removed the click event on load using the $removedHandler in javascript but I've got an error "Sys.InvalidOperationException: Handler was not added through the Sys.UI.DomEvent.addHandler method."

Is there a way to validate if the event handler is already removed? Here's my sample code:

$removeHandler($find('ctl00_ContentPlaceHolder1_aMembersInformation_AccordionExtender').get_Pane(1).header,"click",$find('ctl00_ContentPlaceHolder1_aMembersInformation_AccordionExtender')._headerClickHandler);