Foreign (Bengali) unicode characters cause rendering issues

Description of the problem or steps to reproduce

Open a file with some Bengali text in it and move around a bit with the cursor. Some characters are left behind and even some line numbers disappear temporarily.

You can use this bit from Fedora's chromium-browser.desktop to reproduce the issue:

[Desktop Entry]
Version=1.0
Name=Chromium Web Browser
# ...
Comment[bn]=ইন্টারনেটটি অ্যাক্সেস করুন
# ...

(depending on your browser/fonts it may not render correctly on Github but you should be able to paste it into micro)

Here's a short demonstration of what happens using Asciinema:

I have confirmed this is a micro specific bug rather than something to do with my terminal (or other setup) – I am able to view the same file without issues in the same terminal with other programs (nvim, kakoune, helix).

Specifications

Commit hash: 1231d242 (version 2.0.13-dev.8)
OS: OpenSUSE Tumbleweed
Terminal: happens in all terminals I tried (xterm, terminator, gnome-terminal)

Reproduce the issue in micro using the Bengali text from the report, moving the cursor through the sample while watching stale characters and line numbers. Compare the behavior with the listed terminal editors and inspect micro's terminal rendering path. Done means Bengali text renders correctly without leftover characters or disappearing line numbers.