Bugfix: don't play theme if music off

[damianut]

Otherwise, it causes Access Violation error.

[piotrmacha]

Good point. We should check if the music system is active, but the current code causes a compilation error because s_musicSystemDisabled is an undeclared identifier. I will be able to help with that in the evening today, but if you manage to fix that beforehand, the PR would be ready to merge.

[piotrmacha]

Compilation error

D:\a\zBassMusic\zBassMusic\src\Gothic/Externals.hpp(9): error C2065: 's_musicSystemDisabled': undeclared identifier
D:\a\zBassMusic\zBassMusic\src\Gothic/Externals.hpp(9): error C2065: 's_musicSystemDisabled': undeclared identifier
D:\a\zBassMusic\zBassMusic\src\Gothic/Externals.hpp(9): error C2065: 's_musicSystemDisabled': undeclared identifier
D:\a\zBassMusic\zBassMusic\src\Gothic/Externals.hpp(9): error C2065: 's_musicSystemDisabled': undeclared identifier

[piotrmacha]

@damianut, please make the following changes:

1. Replace s_musicSystemDisabled with zCMusicSystem::s_musicSystemDisabled - this symbol is a static member of zCMusicSystem class, but in external we are outside the class context.
2. Move your if below parser->GetParameter(id); - in externals, we must always pop every parameter from the stack before early return. Otherwise, it would lead to memory leaks or even a crash.

The final code should look like

    int BassMusic_Play()
    {
        zSTRING id;
        parser->GetParameter(id);
        if (zCMusicSystem::s_musicSystemDisabled)
        {
            log->Error("Music system disabled.");
            return 0;
        }
        zCMusicTheme* theme = zmusic->LoadThemeByScript(id);
        zmusic->PlayTheme(theme, zMUS_THEME_VOL_DEFAULT, zMUS_TR_DEFAULT, zMUS_TRSUB_DEFAULT);
        return 0;
    }

[piotrmacha]

As requested by the PR author @damianut, the fixes were made by the project maintainers in #43