firefox-bookmarks flatten --filename error.

Hi and thanks for this nice tool you developed. I get the following error while trying the cli option on windows.

Is it an empty folder maybe?

Thanks a lot, Nikolas

`C:\Users\user\AppData\Roaming\npm\node_modules\firefox-bookmarks\lib\firefox-bookmarks.js:35 var bookmarkFolders = bookmarkMenu.children; ^

TypeError: Cannot read property 'children' of undefined at Function.BookmarkCollection.parse (C:\Users\user\AppData\Roaming\npm\node_modules\firefox-bookmarks\lib\firefox-bookmarks.js:35:38) at new BookmarkCollection (C:\Users\user\AppData\Roaming\npm\node_modules\firefox-bookmarks\lib\firefox-bookmarks.js:10:38) at C:\Users\user\AppData\Roaming\npm\node_modules\firefox-bookmarks\lib\cli.js:63:26 at FSReqWrap.readFileAfterClose [as oncomplete] (fs.js:511:3) `