QTree with children as object triggers error since 2.12

[Tofandel]

What happened?

Since 2.12.0, specifically this commit c6242ba#diff-387b9b62424fed6c9add037b377c07e02f3deca0d50edeb2a415defd12f0e9bbR143

A QTree throws error when nodes have an empty object instead of an empty array

<QTree 
              label-key="name"
              node-key="id"
              :nodes="[{id: 1, name: 'Test', children: {}}]"/>

This is a problem because in PHP json serialization creates objects instead of arrays when your array is empty, which when retrieved from API and used in Quasar, triggers this error

json_encode(['nodes' => [['id' => 1, 'name' => 'Test', 'children' => []]]]) 
=> {"nodes": [{"id": 1, "name": "Test", "children": {}}]}

What did you expect to happen?

No error to be thrown, it should handle the fact that children is not an array

Reproduction URL

https://codepen.io/Tofandel/pen/RwqRwQY

How to reproduce?

1. Go to reproduction link
2. Page is blank and check console for error

Flavour

Quasar CLI with Webpack (@quasar/cli | @quasar/app-webpack)

Additional context

Changing from .length > 0 to .length !== 0 is not equivalent because ({}).length is undefined

([]).length > 0
false
({}).length > 0
false
([]).length !== 0
false
({}).length !== 0
true