Saved SGF file is missing moves after first "pass"

[martinxyz]

Reproduce

1. New game
2. Black stone
3. Pass (via ... menu)
4. Continue game
5. Save SGF
6. Open the SGF file in a text editor

Observe: SGF contains only the first move.

Additional Info

The "save SGF" dialog didn't close automatically after saving (it never does).

Instead of saving the game, I can switch in to Edit or Review mode and step back until I'm hitting the "pass" move. After that, I can no longer step forward. (The forward arrow turns gray at that move.)

When setting up the game with a handicap (two black stones) instead of passing, everything works as expected. (Until a player passes.)

Version 2.5.9 installed via F-Droid on LinageOS (Android 11, without gapps).

[martinxyz]

Setting a stone (GoGame.kt line 184) calls actMove.apply(), which links the move to the parent's next moves. But this linking does not seem to happen for pass() a few lines above.

Probably in order to make redo() work, everything in GoMove.kt needs to be fixed to handle pass moves instead of asserting a non-null position with cell!!.