mScriptObject = nsnull;
nsDOMStyleSheetList::nsDOMStyleSheetList(nsIDocument *aDocument){  NS_INIT_REFCNT();  mLength = -1;  // Not reference counted to avoid circular references.  // The document will tell us when its going away.  mDocument = aDocument;  mDocument->AddObserver(this);  mScriptObject = nsnull;}