Excelize: GetStyle panics on a negative fillId, borderId or fontId in styles.xml

Excelize is a Go language library for reading and writing Microsoft Excel spreadsheets. From 2.8.0 to 2.11.0, GetStyle's fill, border, and font extraction predicates check only upper bounds for attacker-controlled style-table indices. File.GetStyle relies on extractStyleCondFuncs predicates that allow negative FillID, BorderID, and FontID values to reach slice indexing. When a crafted styles.xml supplies a negative fillId, borderId, or fontId and the application reads the style, a negative identifier passes the upper-bound-only predicate and becomes a negative slice index, allowing an attacker to panic while reading cell styling. No fixed version is available as of this review.