Fix feature builds.

src/module/mod.rs

@@ -1,7 +1,6 @@
 //! Module defining external-loaded modules for Rhai.
 
 use crate::ast::FnAccess;
-use crate::func::register::Mut;
 use crate::func::{
     shared_take_or_clone, CallableFunction, FnCallArgs, IteratorFn, RegisterNativeFunction,
     SendSync,
@@ -21,6 +20,9 @@ use std::{
     ops::{Add, AddAssign},
 };
 
+#[cfg(any(not(feature = "no_index"), not(feature = "no_object")))]
+use crate::func::register::Mut;
+
 /// A type representing the namespace of a function.
 #[derive(Debug, Clone, Copy, Eq, PartialEq, Ord, PartialOrd, Hash)]
 #[cfg_attr(feature = "metadata", derive(serde::Serialize))]