Fix NPE when onStopUser.

The default value of mConnection is null, it initializes lazy when we
are serving the first request. Due to no request comes, the mConnection
keeps null which causes NPE.

Bug: 144356634
Test: Manual. Create work profile. Make usre no NPE when stop work profile.
Change-Id: Id656a83989e18ac6f62c1456609bd55e44663914
1 file changed