Fixing out-of-heap error due to large memory copy

[msooseth]

Description

This issue is related to #444. I am fixing it by returning IllegalOverflow, which is what we already do, although we only check $2^{64}$, not 2^{28}$. However, it's mostly the same thing -- way too large of a number.

Checklist

• [x] tested locally
• [ ] added automated tests
• [ ] updated the docs
• [x] updated the changelog

[msooseth]

Thanks for the review!