rv = shell->GetDocument(aDocument);
if (shell) rv = shell->GetDocument(aDocument);
NS_IMETHODIMP nsPluginInstanceOwner::GetDocument(nsIDocument* *aDocument){  nsresult rv = NS_ERROR_FAILURE;  if (nsnull != mContext) {    nsCOMPtr<nsIPresShell> shell;    mContext->GetShell(getter_AddRefs(shell));    rv = shell->GetDocument(aDocument);  }  return rv;}