Fix `s_summary` return for empty logical vectors #1600

All 771 tests pass, 9 skipped in 1m 16s

      1 files ±0     80 suites ±0 1m 16s ⏱️ +4s
  780 tests ±0   771 ✔️ ±0     9 💤 ±0 0 ❌ ±0
1 657 runs ±0 1 040 ✔️ ±0 617 💤 ±0 0 ❌ ±0

Results for commit df9261a. ± Comparison against earlier commit 41d9796.