[MU4 Issue] Disable ability to make panels disappear from re-sizing them

[rich777300]

Describe the bug You can undock a panel/toolbar and drag to resize it such that it disappears.

To Reproduce Steps to reproduce the behavior:

1. Undock any panel you like.
2. Resize it so it disappears.

Expected behavior There is a minimum width and/or height so that this does not happen.

Platform information

• OS: Windows 10 64-bit

Additional context It will still display as 'open' (ie checkmarked) in the view panel however.

You can 'get the panel back,' so to speak, by unchecking then rechecking it in the view panel, or closing the score and re-opening it (where I assume the saved workplace re-opens/re-displays the panel.)

You can also get the panel back by restoring the default layout in the view panel too - forgot to include in video.

https://user-images.githubusercontent.com/102642087/210184886-7866bcf7-82f1-4db0-974c-1cfb148c674c.mp4