Fix missing observation. #9409

Job	Run time
base-tests (./cli)	2m 50s
benchmark (e10_drive)	3m 30s
base-tests (./envision)	3m 10s
examples-rl (e10_drive)	3m 0s
benchmark (e11_platoon)	3m 26s
base-tests (./smarts/core --nb-exec-timeout 65536 --ignore=./smarts/core/tests/test_notebook.py)	3m 10s
examples-rl (e11_platoon)	2m 55s
base-tests (./smarts/env --ignore=./smarts/env/tests/test_rllib_hiway_env.py)	3m 9s
base-tests (./smarts/env/tests/test_rllib_hiway_env.py)	3m 3s
base-tests (./smarts/sstudio)	3m 8s
base-tests (./smarts/ray)	3m 8s
base-tests (./examples/tests/test_examples.py)	3m 11s
	37m 40s

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