Freezer: Can't add node to the tree. It's already added and freezer is configured to `singleParent: true`

[djhr]

When running the following code freezer correctly warns about calling remove on a detached node

const data = {
  a: {
    aa: {},
    ab: {},
    ac: {},
    ad: {}
  },
};

const store = new Freezer(data, {singleParent: true});

const a = store.get().a;
a.remove('aa');

setTimeout(() => {
  a.remove(['ab', 'ac', 'ad']);
}, 500);

WARNING: Method object.remove called on a detached node. { aa: {}, ab: {}, ac: {}, ad: {} } [ 'ab', 'ac', 'ad' ]

However if data has a property b, the exact same code will make freezer throw an error

const data = {
  a: {
    aa: {},
    ab: {},
    ac: {},
    ad: {}
  },
  b: {},
};

const store = new Freezer(data, {singleParent: true});

const a = store.get().a;
a.remove('aa');

setTimeout(() => {
  a.remove(['ab', 'ac', 'ad']);
}, 500); 

/Users/djhr/Desktop/freezer/node_modules/freezer-js/src/frozen.js:407
                                throw new Error("Freezer: Can't add node to the tree. It's already added and freezer is configured to `singleParent: true`.");
                                ^

Error: Freezer: Can't add node to the tree. It's already added and freezer is configured to `singleParent: true`.
    at Object.addParent (/Users/djhr/Desktop/freezer/node_modules/freezer-js/src/frozen.js:407:11)
    at /Users/djhr/Desktop/freezer/node_modules/freezer-js/src/frozen.js:319:8
    at Object.each (/Users/djhr/Desktop/freezer/node_modules/freezer-js/src/utils.js:44:5)
    at Object.refresh (/Users/djhr/Desktop/freezer/node_modules/freezer-js/src/frozen.js:312:9)
    at Object.refreshParents (/Users/djhr/Desktop/freezer/node_modules/freezer-js/src/frozen.js:385:10)
    at Object.remove (/Users/djhr/Desktop/freezer/node_modules/freezer-js/src/frozen.js:164:8)
    at Object.notify (/Users/djhr/Desktop/freezer/node_modules/freezer-js/src/freezer.js:72:33)
    at Object.remove (/Users/djhr/Desktop/freezer/node_modules/freezer-js/src/nodeCreator.js:153:27)
    at Timeout._onTimeout (/Users/djhr/Desktop/freezer/test.js:20:5)
    at listOnTimeout (internal/timers.js:549:17)

I would expect freezer not to throw an error about adding nodes, code is only removing. Instead I would expect freezer to warn about the remove on a detached node.