Prevent all node to be checked when filtering tree

[dpellier]

See #196

There is a strange behaviour for the leaf node.

On first render, there are correctly set as a leaf with a children: undefined property.

But after filtering, they got a children: [] prop.

Thus the isLeaf value is set wrong (which you can see on the filter example, when filtering the leaf suddenly get a directory icon).
And it also changes the returned values of the checked function, checking everything (even if the actual checked state is still untouched).

[MaxwellKendall]

@dpellier @jakezatecky I am also having this bug.

I've confirmed this branch fixes the issue. 🙏

Opened a PR on your branch to update breaking tests: dpellier#2

[olessiap]

yess, so pumped there's a fix already in place for this one!

[vjr12]

@jakezatecky this issue still persists. Merge the PR?

[jalalazimi]

Hi friends, Please check out #217 .
Replace filtered.push({ ...node, children }); with filtered.push({...node, ...children.length && {children}});. Temporary you can use this solution to fix the above issue.