container.Base: mergeConfig() is causing issues in the latest version

regression issue.

old code:

    mergeConfig(...args) {
        let me     = this,
            config = super.mergeConfig(...args);

        // avoid any interference on prototype level
        // does not clone existing Neo instances

        if (config.itemDefaults) {
            me._itemDefaults = Neo.clone(config.itemDefaults, true, true);
            delete config.itemDefaults
        }

        if (config.items) {
            me._items = Neo.clone(config.items, true, true);
            delete config.items
        }

        return config
    }

new code:

    mergeConfig(...args) {
        let me     = this,
            config = super.mergeConfig(...args);

        // avoid any interference on prototype level
        // does not clone existing Neo instances

        if (config.itemDefaults) {
            me._itemDefaults = Neo.clone(config.itemDefaults, true, true);
            delete config.itemDefaults
        }

        if (config.items) {
            // If we are passed an object, merge the class's own items object into it
            me.items = Neo.typeOf(config.items) === 'Object' ?
                Neo.merge(Neo.clone(me.constructor.config.items), config.items) : config.items;
            delete config.items
        }

        return config
    }

while we do have a new beforeSetItems() method, the initial cloning part got lost.