NPE happens when there is an orphaned session which we've
tried to prevent in all cases.
Log an error message if this situation happens.
Bug: 227342978
Test: atest CtsRootPackageInstallerHostTestCases
Change-Id: Ia21323926bd9db1a6f05461904deb45b4c3dd0bc
(cherry picked from commit 07e31dfb1e)
Merged-In: Ia21323926bd9db1a6f05461904deb45b4c3dd0bc