Fix bug #13744434 Stability: ISE in Settings: Can't switch to header...

..that has no Fragment nor Intent at SettingsActivity.onHeaderClick(SettingsActivity.java:654)

- satisfy the Monkeys has they were able to click on "WIRELESS &
NETWORK" header which is a Category and normally non clickable...
(so probably a race condition)

Change-Id: Ia33d2b6e55e910409a566e5f05c1e3bae8008807