mRS could be null when lock and unlock screen by pressing power key
several times, it causes RsBalls crash. Add null pointer check to fix.
Change-Id: If37dee8609420daaff17772d5194cad5531f98e6
Author: Yong Chen <yong.a.chen@intel.com>
Signed-off-by: Yong Chen <yong.a.chen@intel.com>
Singed-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: 31271
da1c93ae4d