Fix NPE 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 07e31dfb1efabc8110d64819f26a06e12a35e020) Merged-In: Ia21323926bd9db1a6f05461904deb45b4c3dd0bc (cherry picked from commit 18179a8762ba14c44d287e853c9a1c38a3dfdddb) Merged-In: Ia21323926bd9db1a6f05461904deb45b4c3dd0bc