items is not created if there is no template (as child template)

Following up #63, even if items property is explicitly defined in child element, it won't be created if template property is not set. For example:

//(somewhere inside a template):
...
  list : {
     show : false,
     items : []
  }

The above doesn't work (list.items is undefined), but the following does:

  list : {
     show : false,
     template : { li : {} }
  }

When template is specified, the property items (array) is created as expected.