Fix for error in IE 8/9: check swfobject exists before attempting to clean it up.

When cleaning up in IE 8/9 (ie. when refreshing the page) swfobject is throwing an error. It tries to delete the global swfobject object - but it hasn't been created as we are using require.js to include the module.  This fix just checks that the object exists before deleting it and any children.