investigate downstream breaking changes in chevron, initialize NA values

[shajoezhu]

  ══ Failed tests ════════════════════════════════════════════════════════════════
  ── Failure ('test-aet05_all.R:6:3'): aet05_all can handle NA values ────────────
  `run(aet05_all, proc_data)` produced warnings.
  ── Failure ('test-aet05_all.R:20:3'): aet05_all can handle some NA values ──────
  `run(aet05_all, proc_data)` produced warnings.
  ── Failure ('test-aet05_all.R:23:3'): aet05_all can handle some NA values ──────
  `run(aet05_all, proc_data, conf_level = 0.9, conf_type = "byar")` produced warnings.
  ── Failure ('test-aet05.R:6:3'): aet05 can handle NA values ────────────────────
  `run(aet05, proc_data)` produced warnings.
  ── Failure ('test-aet05.R:23:3'): aet05 can handle some NA values ──────────────
  `run(aet05, proc_data)` produced warnings.
  ── Failure ('test-aet05.R:26:3'): aet05 can handle some NA values ──────────────
  `run(aet05, proc_data, conf_level = 0.9, conf_type = "byar")` produced warnings.

[edelarua]

Warnings should be fixed by 8fb5968

[shajoezhu]

Many thanks @edelarua