fix `as_result_df` for nested `rbind` #925

All 201 tests pass in 1m 36s

1 files ±0 24 suites ±0 1m 36s ⏱️ +5s
201 tests ±0 201 ✅ +1 0 💤 - 1 0 ❌ ±0
1 524 runs +2 1 524 ✅ +3 0 💤 - 1 0 ❌ ±0

Results for commit 8e27408. ± Comparison against earlier commit c760e99.