Fix example_asset_store consumer crash and test comment typos

[kaxil]

Fallout from the task_state->task_store rename (#67833):

• example_asset_store consume() fell back to the string "{}" when the asset had no last_run_summary yet, then called .get() on it, raising AttributeError. Fall back to an empty dict so .get() works.
• A eager find-replace turned "statement(s)" into "Storement(s)" in two comments in test_context.py. Restored the original words.

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[amoghrajesh]

Ah thank you!