public String toString() {
        if (closure != null) {
            return "Callframe at: " + closure.toString();
        }
        if (javaFunction != null) {
            return "Callframe at: " + javaFunction.toString();
        }
        return super.toString();
    }
This ensures that top is at least as high as index, and that everything from index and up is empty.
@param index
main/src/main/java/cgeo/geocaching/wherigo/kahlua/vm/LuaCallFrame.java