CVE-2024-37820: PingCAP TiDB nil pointer dereference

The key vulnerability stems from the ColumnSubstituteImpl function's handling of NewFunctionInternal calls. The original code (vulnerable version) directly returned NewFunctionInternal without error checking. The patch replaces this with NewFunction with error handling, indicating that the nil return from failed function creation was the root cause. The stack trace shows the panic occurs in inferCollation() when processing expressions substituted by this function. The commit specifically addresses this code path by adding error propagation to prevent nil values from being used in subsequent operations.