JavaScript error when assuming currentChapter() always returns something

[Siderite]

Repro steps:

1. Create a new study with a default chapter
2. Delete the only chapter it has

Error:

/study/ydFN5F9w/CZQsfO8R - Uncaught TypeError: Cannot read properties of undefined (reading 'players') - (https://lichess1.org/assets/compiled/lib.M3FAU267.js:6:39929)
TypeError: Cannot read properties of undefined (reading 'players')
    at Object.Is (lib.M3FAU267.js:6:39929)
    at Qo (lib.M3FAU267.js:6:33712)
    at $h (lib.M3FAU267.js:6:64375)
    at lib.7SYXJDC4.js:1:2120
    at Xt.G [as redraw] (lib.7SYXJDC4.js:1:3497)
    at changeChapter (lib.M3FAU267.js:6:87780)
    at Xt.socketHandler (lib.M3FAU267.js:6:85541)
    at Object.receive [as socketReceive] (lib.M3FAU267.js:5:43297)
    at Object.receive (analyse.study.LTIO4XE2.js:1:1512)
    at handle (lib.SFPXEOLA.js:2:2286)

The line in question is this:

lila/ui/analyse/src/study/playerBars.ts

Line 20 in e7eaf64

const players = study.currentChapter().players,

In this situation, currentChapter() doesn't return anything.

[kraktus]

I'm pretty sure you cannot have a study with a chapter, and when deleting the only one, the server recreate another just after.

[Siderite]

Yes, in the meanwhile the JavaScript fails.

[ornicar]

Create a new study with a default chapter
Delete the only chapter it has

didn't reproduce the bug for me

[yafred]

didn't reproduce the bug for me

Same for me.
If I delete the only chapter, there is immediately a new chapter (Chapter 1) and nothing in the javascript console.
I tried with and without Lichess tools extension enabled

[Siderite]

LT disabled from extensions. Could it be specific to Brave?

[Siderite]

Firefox: