RUSTSEC-2021-0028

When inserting rows from an iterator at a particular index, `toodee` would shift items over, duplicating their ownership. The space reserved for the new elements was based on the `len()` returned by the `ExactSizeIterator`.

This could result in elements in the array being freed twice if the iterator panics. Uninitialized or previously freed elements could also be exposed if the `len()` didn't match the number of elements.

These issues were fixed in commit `ced70c17` by temporarily setting the length of the array smaller while processing it and adding assertions on the number of elements returned by the iterator.