Fix added/removed bytes being visually misaligned in data diff view

[LagoLunatic]

diff.len / 8 doesn't always catch when the 8-byte column midpoint is passed since e.g. when cur_addr=4 diff.len=5 neither one of those are greater than 8 individually, but are combined.

Before:

After:

[encounter]

Thank you! This has long annoyed me (and I’m sure others 🙂)