fix: fix off by one bug

[dwootton]

Depending on when the recording is cutoff, there can be an off-by-one error causing the induction step to crash. This PR introduces a check to ensure the index is in range.

Error when I ran get_human_trajectory.py before fix:

`
{'before': '../records/screenshots/176348359
4.60252_scroll(806.9, 425.4, dx=0.00,
dy=-3.00)_before.jpg', 'after': '../records/
screenshots/1763483594.62327_scroll(806.9,
425.4, dx=0.00, dy=-3.00)_after.jpg'}

Original trajectory: #14 steps.
Traceback (most recent call last):
File
"/Users/dwootton/workflow-induction-toolkit/
workflow-induction/get_human_trajectory.py",
line 356, in
main()
File
"/Users/dwootton/workflow-induction-toolkit/
workflow-induction/get_human_trajectory.py",
line 292, in main
if states[i+1]["before"] is None or
states[i+1]["after"] is None:`