message: refactor: remove unnecessary checks
diff: @@ -111,9 +111,8 @@ function initProps (vm: Component, propsOptions: Object) {
  function initData (vm: Component) {
  let data = vm.$options.data
  - data = vm._data = typeof data === 'function'
  - ? getData(data, vm)
  - : data || {}
  + // $options.data is guaranteed to be a function after merge
  + data = vm._data = getData(data, vm)
  if (!isPlainObject(data)) {
  data = {}
  process.env.NODE_ENV !== 'production' && warn(
  