When there's only one feed in a category, the importer fails on line 33. in that case, $group['outline'] is not an array, but has only one child $group['outline']['@attributes']
<?xml version="1.0" encoding="UTF-8"?>
<opml version="1.0">
<head>
<title>ubscriptions in feedly Cloud</title>
</head>
<body>
<outline text="Comics" title="Comics">
<outline type="rss" text="Chief O'Brien At Work" title="Chief O'Brien At Work" xmlUrl="http://chiefobrienatwork.com/rss" htmlUrl="http://chiefobrienatwork.com/"/>
</outline>
<outline text="Fun" title="Fun">
<outline type="rss" text="The Oatmeal - Comics, Quizzes, & Stories" title="The Oatmeal - Comics, Quizzes, & Stories" xmlUrl="http://feeds.feedburner.com/oatmealfeed" htmlUrl="http://theoatmeal.com/"/>
<outline type="rss" text="xkcd.com" title="xkcd.com" xmlUrl="http://xkcd.com/atom.xml" htmlUrl="https://xkcd.com/"/>
</outline>
</body>
</opml>