Settings: Fix NPE in QS on tablets

On tablets, onCreate is only called once, while onActivityCreated is called every
time the fragment is visible. So a second remove of a preferent will result in a NPE

Change-Id: I30205380018f29bd99270c707bd4f8ba03103648
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>
Merge remote-tracking branch 'cm/cm-10.2' into cm-10.2
Revert "Quick Settings: Fix tiles and layout back button FC"

This reverts commit b0b6584b241013e38c219791680c269b8ce9965a.
Merge remote-tracking branch 'sgt7/cm-10.2' into cm-10.2-sgt7