Unsafe casting in getItems() method

[Touchie771]

Issue Description

The getItems() method in Menu.java performs an unsafe cast from Collections.unmodifiableSet() to HashSet<SlotItem>. This could cause ClassCastException at runtime.

Location

Menu.java line 148

Current Code

public HashSet<SlotItem> getItems() {
    return (HashSet<SlotItem>) Collections.unmodifiableSet(this.items);
}

Suggested Fix

Change the return type to Set<SlotItem>:

public Set<SlotItem> getItems() {
    return Collections.unmodifiableSet(this.items);
}

Impact

This is a bug waiting to happen - users expecting a mutable HashSet might get unexpected runtime errors when trying to use HashSet-specific methods.