Panel should remember sizing before toggling editor area

[alexr00]

Testing #78137

1. Open a folder
2. Close all editors
3. Close the panel
4. Run the Toggle Editor Area command
5. The panel takes over ✔
6. Open a file by clicking in the explorer.
7. See that the panel ends up a weird size:

[RMacfarlane]

I'm able to reproduce this in the latest insiders, 8cd00a7

[alexr00]

I'm still seeing this in bffbe2e. Same repro steps on Windows.

[sbatten]

I deleted a line that was definitely necessary for this to work ><