All nodes are checked on filter

[chumarie]

Describe the bug
Hello, I have got troubles when I filter the nodes with the search bar. All the checkboxes are checked are can't be unchecked, until filterText il cleared

Reproduction steps
Tried with your FilterExample.js

Expected behavior
Any checked checkboxes, excepting if they are presents in checked state

Screenshots

[javiercaceres]

Also, leaves are shown as a parent folder after filtering. Part of the problem is here:

react-checkbox-tree/src/js/NodeModel.js

Lines 165 to 167 in 815285c

	isEveryChildChecked(node) {
	return node.children.every((child) => this.getNode(child.value).checked);
	}

And here:

react-checkbox-tree/src/js/CheckboxTree.js

Lines 195 to 199 in 815285c

	isEveryChildChecked(node) {
	return node.children.every(
	(child) => this.state.model.getNode(child.value).checkState === 1,
	);
	}

.every acts like the "for all" quantifier in mathematics. In particular, for an empty array, it returns true. Leaves with an empty "children" property will be displayed as checked.