PanelMenu shows top level entries with the label underlined

[rferrerasm]

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[*] bug report => Search github for a similar issue or PR before submitting
[ ] feature request => Please check if request is not on the roadmap already https://github.com/primefaces/primeng/wiki/Roadmap
[ ] support request => Please do not submit support request here, instead see http://forum.primefaces.org/viewforum.php?f=35

Plunkr Case (Bug Reports)

http://plnkr.co/edit/UK89QRhhGgSDT76SZJEB?p=preview

Current behavior

The top level menu entries of a PanelMenu show the label text underlined in the free themes.

Expected behavior

The text shouldn't be underlined.

Minimal reproduction of the problem with instructions

Check the supplied Plunkr.

Please tell us about your environment:

• Angular version: 4.3.1

• PrimeNG version: 4.1.2

• Browser: IE 11, Firefox 54, Chrome 60.