Game overrides don't save "custom_viewport_height"

Description

Game overrides don't save "custom_viewport_height". It does save any other settings, but at least when there's a core override preceding it, the vertical scaling it's not writen on the game's cfg file, having to externally navigate to the cfg, and write the "custom_viewport_height" desired manually.

Expected behavior

"custom_viewport_height" Value should be writen when saving game overrides, just as horizontal scaling (and any other setting) does.

It would also be helpful to be able to manually save and load a custom override, or any override already saved, to not have to change scaling/overlay settings for every game that has a different screen disposition, as it's the case for most arcade games.

Actual behavior

I have, for example, set up the Beetle Wonderswan core, with a custom screen scale to fit an horizontal playing field as the core override, as it's the most common layout.

I made a vertical overlay, and in a vertical playing game, I modified the both horizontal and vertical scaling to fit a vertical layout, and saved the game's override. Opened the game again and everything was the way I saved minus the vertical scale. Did everything again and the result was the same, deleted the Beetle Wonderswan cfg folder so I could configure all from a fresh start and ended up with the same result. Then, opened the game's cfg file I saved with a text editor and realized the "custom_viewport_height" wasn't there at all. After adding the line manually, opened the game and the scaling was the way I wanted.

Steps to reproduce the bug

1. In a core, once ingame, change screen scaling, save core overrides and close the game.
2. Open another game within the same system/core, change to a different screen scale, both horizontally and vertically. Save game overrides and close the game.
3. Open last game again and all settings saved with the game override are intact, except vertical scaling, defaulting to the core override's value.

Version/Commit

• RetroArch v1.10.0

• OS: Windows 10 64 bits.

No source file or test is named; start by reproducing the core-override and game-override sequence described, then inspect how custom_viewport_height is written to the game's cfg file. Done means the vertical scale is present in the saved game override and remains correct after reopening the game, without changing the core override.