AGS: Crash in Heatwave at the start of the game

[criezy]

When starting Heatwave, a crash occurs just before displaying the menu screen after the Scavenger logo video finish playing:

ERROR: !Error running function 'room_AfterFadeIn':
Error (line 11): Null pointer referenced!

Game: ​https://www.adventuregamestudio.co.uk/site/games/game/1737-heatwave/
ScummVM version: current master from Monday April 24 (b329c674c7059dab71c4f7650d79edc1470c0d06)
Platform: macOS Monterey on M1 computer
Callstack:

    frame #11: 0x00000001001bda90 scummvm`AGS3::quitprintf(fmt="!Error running function '%s':\n%s") at common.cpp:42:2
    frame #12: 0x000000010076dd44 scummvm`AGS3::quit_with_script_error(functionName="room_AfterFadeIn") at script.cpp:578:3
    frame #13: 0x0000000100766b48 scummvm`AGS3::RunScriptFunction(sci=0x000000012e096080, tsname="room_AfterFadeIn", numParam=0, params=0x0000000000000000) at script.cpp:366:3
    frame #14: 0x000000010076f54c scummvm`AGS3::RunScriptFunctionInRoom(tsname="room_AfterFadeIn", param_count=0, params=0x0000000000000000) at script.cpp:399:14
    frame #15: 0x000000010076ce9c scummvm`AGS3::RunScriptFunctionAuto(sc_inst=kScInstRoom, tsname="room_AfterFadeIn", param_count=0, params=0x0000000000000000) at script.cpp:435:10
    frame #16: 0x000000010076b750 scummvm`AGS3::QueueScriptFunction(sc_inst=kScInstRoom, fn_name="room_AfterFadeIn", param_count=0, params=0x0000000000000000) at script.cpp:282:3
    frame #17: 0x000000010076b3b8 scummvm`AGS3::run_interaction_script(nint=0x000000013013d010, evnt=7, chkAny=-1) at script.cpp:190:3
    frame #18: 0x0000000100401a4c scummvm`AGS3::process_event(evp=0x0000000107cb01d4) at event.cpp:181:4

The game starts properly in upstream AGS. So either the issue has been fixed there already, of this is a ScummVM-specific issue.

[i30817]

Upstream had a long discussion about a bug with fadeout (room exit), namely it was being done wrong and characters disappeared before the fadeout.

Although that was supposed to be a AGS 4 fix, and 'fadeout' not 'fadein' so maybe it's not the same problem. But the author made a lot of commits because of this issue (to fix bugs he found) so maybe some commit triggered or fixed a bug.

​https://github.com/adventuregamestudio/ags/issues/1970

A new api for transitions callbacks is supposed to be introduced for AGS4 but i think scummvm doesn't plan to add support for that new engine.

[tag2015]

This was a scummvm-only issue related to the partially implemented mod playback.

Fixed in ​54c57bb