Use typed constant index conversion in script validation

Assisted-by: OpenAI Codex:model identifier unavailable

crates/vm/src/vm/crossinterp.rs

@@ -843,7 +843,7 @@ pub(crate) fn code_returns_only_none(code: &Py<PyCode>) -> bool {
             Instruction::LoadCommonConstant { idx } => idx.get(arg) == CommonConstant::None,
             Instruction::LoadConst { consti } => code
                 .constants
-                .get(consti.get(arg) as usize)
+                .get(usize::from(consti.get(arg)))
                 .is_some_and(|value| matches!(value.borrow_constant(), BorrowedConstant::None)),
             _ => false,
         };