Fix bug with partial path

[Kawaizombi]

Currently, when you pass paths like this

pathListToTree([
  'test/nested',
  'test'
])

where secondary path are partial of first one the result will have node with undefined name

[
  {
    "name": "test",
    "children": [
      {
        "name": "nested",
        "children": []
      },
      {
        "name": undefined, // <- THIS ONE
        "children": []
      }
    ]
  }
]