Revert "initialise vectors to zero"

[sbfnk]

This reverts commit dcbd3ae.

This is to test whether this commit is behind the current test failures on windows.

[github-actions]

This is how benchmark results would change (along with a 95% confidence interval in relative change) if fad4ebb is merged into main:

• ❗🐌default: 1.07m -> 1.2m [+1.89%, +21.4%]
• ❗🐌no_delays: 1.05m -> 1.28m [+6.26%, +36.57%]
•   :ballot_box_with_check:random_walk: 19.9s -> 22.1s [-1.38%, +24.12%]
•   :ballot_box_with_check:stationary: 40.6s -> 43.6s [-4.66%, +19.22%]
•   :ballot_box_with_check:uncertain: 1.53m -> 1.64m [-9.65%, +23.82%]
  Further explanation regarding interpretation and methodology can be found in the documentation.

[sbfnk]

This fixed the windows error on first attempt and re-exposed it upon re-running. Might be worth testing again.