[BUG] resizing window forgets read state; when image visible everything flickers

[margusp]

Describe the bug

When resizing the window, you are taken back to some (random?) old message in the chat history. Also when there is an image visible in the chat and you try to resize the window, everything flickers.

Environment

• Device: computer with macOS
• OS version: Big Sur 11.2
• Tact version: 1.2 (89)

To reproduce

Steps to reproduce the behavior:

1. Go to a chat
2. Resize the window with pointer

Expected behavior

You stay in the same last read state where you began and everything doesn't flicker like crazy.

Observed behavior

See screen recording.

Screenshots, logs, etc

Screen recording: https://www.dropbox.com/s/jvzxhkk4zhzl04i/Screen%20Recording%202021-02-09%20at%2010.21.04.mov?dl=0

[jaanus]

See also #57, related but different windowing-related bug.