AGS: Crash when exiting Mage's Initiation

[criezy]

When we start Mage's Initiation and select the Quit option from the game menu, ScummVM crashes with a buffer overflow in

#0 in AGS3::ExecutingScript::init() executingscript.cpp:83
#1 in AGS3::PrepareTextScript(AGS3::ccInstance*, char const**) script.cpp:314
#2 in AGS3::RunScriptFunctionIfExists(AGS3::ccInstance*, char const*, int, AGS3::RuntimeScriptValue const*) script.cpp:349
#3 in AGS3::run_claimable_event(char const*, bool, int, AGS3::RuntimeScriptValue const*, bool*) event.cpp:72
#4 in AGS3::RunTextScript2IParam(AGS3::ccInstance*, char const*, AGS3::RuntimeScriptValue const&, AGS3::RuntimeScriptValue const&) script.cpp:435
#5 in AGS3::RunScriptFunction(AGS3::ScriptInstType, char const*, unsigned long, AGS3::RuntimeScriptValue const&, AGS3::RuntimeScriptValue const&) script.cpp:265
#6 in AGS3::QueueScriptFunction(AGS3::ScriptInstType, char const*, unsigned long, AGS3::RuntimeScriptValue const&, AGS3::RuntimeScriptValue const&) script.cpp:258
#7 in AGS3::run_on_event(int, AGS3::RuntimeScriptValue&) event.cpp:87
#8 in AGS3::gui_on_mouse_down(int, int) gui.cpp:659
#9 in AGS3::check_mouse_controls() game_run.cpp:227
#10 in AGS3::check_controls() game_run.cpp:507
#11 in AGS3::game_loop_check_controls(bool) game_run.cpp:554
#12 in AGS3::UpdateGameOnce(bool, AGS3::AGS::Engine::IDriverDependantBitmap*, int, int) game_run.cpp:727
#13 in AGS3::GameTick() game_run.cpp:865
#14 in AGS3::RunGameUntilAborted() game_run.cpp:956

The issue is that in PrepareTextScript it start using more script than allocated in the Globals::_scripts array

	_G(scripts)[_G(num_scripts)].init();
	_G(scripts)[_G(num_scripts)].inst = sci;
	...
	_G(num_scripts)++;

In the original it never use more than one script at a time on this title screen. In ScummVM that is also the case until we click on Quit, and then it starts using more and more scripts until it crashes.

[criezy]

This might have the same cause as #12461.

[dreammaster]

Thanks for doing the analysis, and pointing out the possible duplicate. It turned out to be that the original has the "quit" method halt the program by calling SDL_Quit, whereas for ScummVM I have to have a bunch of "if (_G(abort_engine)) return -1" in various places to allow a graceful break out of the game loop (since we don't allow exceptions in engines yet). Turns out I needed to add a few more.