if ((nsnull != mDocument) && (mDisabled != oldState)) {
if (mDocument && (mDisabled != oldState)) {
CSSStyleSheetImpl::SetDisabled(PRBool aDisabled){  PRBool oldState = mDisabled;  mDisabled = aDisabled;  if ((nsnull != mDocument) && (mDisabled != oldState)) {    mDocument->SetStyleSheetDisabledState(this, mDisabled);  }  return NS_OK;}