Constant SOUNDSET_UNASSIGNED 

pub const SOUNDSET_UNASSIGNED: u16 = 0xFFFF;

SoundSetFile’s “nothing assigned” sentinel.

The label reads like a resref and is not one: it is a soundset.2da row index read as a WORD, and the constructor sets -1. Row 0 is a real soundset, so a zero fallback assigns every creature the first row in the table rather than leaving it unassigned.

Fourth in a family that keeps producing the same defect, alongside PORTRAIT_ID_USE_RESREF, TRAP_TYPE_ABSENT and the encounter’s object references. A “nothing assigned” sentinel in this engine is almost never zero, because zero is a valid row in whatever table the field indexes.