BiometricScheduler: fix the NPE problem in startWatchdog method.

Binder thread call the startWatchdog,but another put the  mCurrentOperation to null when when assigning value to the operation object.This may cause NPE problems.

Test: OEM monkey test
Flag: EXEMPT bugfix
Bug: 379003855
Change-Id: Ib44e3214c891dc4e975d34e1c4213faea14131c6
1 file changed