[dev] Buildings display method CM.Disp.UpdateBuildings throws an error in sell mode

[Chorizorro]

⚠️ This bug concerns the dev branch, not the actual 2.031.1 release ⚠️

When switching to "Sell" mode for buildings, the JS console starts throwing this error at each Game loop execution:

Uncaught TypeError: can't convert undefined to object
    UpdateBuildings http://localhost/cookiemonster/CookieMonster.js:1401
    Loop http://localhost/cookiemonster/CookieMonster.js:3336
    Loop http://localhost/cookiemonster/CookieMonster.js:3246
    setTimeout handler*Game.Launch/Game.Loop https://orteil.dashnet.org/cookieclicker/main.js?v=2.089:14457
    Loop http://localhost/cookiemonster/CookieMonster.js:3245
    setTimeout handler*Game.Launch/Game.Loop https://orteil.dashnet.org/cookieclicker/main.js?v=2.089:14457
    Loop http://localhost/cookiemonster/CookieMonster.js:3245
    // [...] Lines after this are irrelevant, it's a repeat of Loop / setTimeout
CookieMonster.js:1401:19

This has been most likely introduced in d40f90d from #340
I could reproduce it in both "Sort Buildings: Default" and "Sort Buildings: PP" mode.

[DanielNoord]

Fixed!
Also stopped sell mode column sorting by PP. This will now always sort by id.