Excelize: Unchecked pivot-cache field index in extractPivotTableFields causes unrecoverable panic

Excelize is a Go language library for reading and writing Microsoft Excel spreadsheets. From 2.8.1 to 2.11.0, separately parsed pivot-table field indices are used to index the pivot-cache field-name slice without bounds checks. extractPivotTableFields uses getPivotCacheFieldsName output while processing GetPivotTables and trusts the dataField fld attribute as an index. When a crafted workbook supplies a pivot-field count mismatch or an out-of-range dataField fld value before GetPivotTables is called, the unchecked index causes a Go slice-bounds panic that escapes the library, allowing an attacker to crash the process or request worker. No fixed version is available as of this review.