Settings: Check Null Pointer Activity in InstalledAppDetails.initiateClearUserData().

If Fragment doesn't attach to one Activity
getActivity() will return null. So we need to check it.

Change-Id: I22e2300dba962b878faa0b2d16feb839554883fa
Author: Jianchun Shen <jianchunx.shen@intel.com>
Signed-off-by: Jianchun Shen <jianchunx.shen@intel.com>
Signed-off-by: Shuo Gao <shuo.gao@intel.com>
Signed-off-by: Bruce Beare <bruce.j.beare@intel.com>
Signed-off-by: Jack Ren <jack.ren@intel.com>
Author-tracking-BZ: 63725