[automerger] Return error for invalid st/lt sps parameters am: b93923e288 am: 797c104f3b am: 092cd28d04 am: 0e0458c8da am: 400d114e64 am: fa6d5fe71f am: 03831de632 am: 1a661cfc0e am: 8151a909f7 am: a9a51a4940 am: a4d67a58e8
am: 4c942bb330

Change-Id: I45d117e62a4effacc1dbed0bc598d55deb8d2fae