desktop ex: fix compilation warning
desktop ex: fix compilation warning

warning C4715: 'TabBar::navigationShortcut' : not all control paths return a value

communi/communi-desktop,communi/communi-symbian,jpnurmi/communi-desktop,communi/communi-symbian,sevanteri/communi-desktop,gdamjan/communi-desktop,communi/communi-symbian,communi/communi-symbian,communi/communi-desktop