Scrolling changes visual appearance of buffer contents

[izuzak]

Describe the bug

It seems that scrolling past the last visible line somehow affects lines with leading tabs -- the tabs get replaced with the contents of the most recent line without leading tabs.

To Reproduce

Steps to reproduce the behavior:

1. ad Makefile
2. press j a few times and scroll down past the last visible line a few times
3. notice how lines with leading tabs changed (e.g. line 9 in GIF below) -- instead of leading tabs they now have the tabs replaced with the content of the most recent line without leading tabs
4. press k a few times and scroll up past the first visible line
5. notice how the contents in now back to normal -- we see tabs again

Expected behavior

Scrolling doesn't affect how buffer contents is displayed

Screenshots

Versions & OS Details

OS: macOS 15.2 (24C101)
ad Version: built from source, commit da57f60