engine can be switched on for an illegal position using the L-shortcut

[glbert-does]

Exact URL of where the bug happened

https://lichess.org/analysis/fromPosition/rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBKKBNR_w_KQkq_-_0_1

source: https://lichess.org/forum/lichess-feedback/stockfish-is-broken-3

i am personally not convinced this is worth fixing, but i will leave it to an actual dev.

Steps to reproduce the bug

1. go to https://lichess.org/analysis/fromPosition/rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBKKBNR_w_KQkq_-_0_1
   (note that this position has two white kings, and is illegal)
2. the engine says "Engine cannot analyse this game" and you cannot activate it via click. however, you can still activate it by pressing the "L"-key.

What did you expect to happen?

i expected the engine to not be activated.

What happened instead?

the engine was activated and gave useless numbers.

Operating system

Ubuntu, but presumably not os dependent

Browser and version (or alternate access method)

works at least in firefox 134 and chromium.

Additional information

No response