Force TreeListView scrollbars to create handles on startup. Closes #202
Force TreeListView scrollbars to create handles on startup. Closes #202

* I honestly don't know why this fixes it really. I finally got a
  reliable repro which involved somehow scrollbars becoming visible and
  creating their window handles in a weird circumstance while dragging
  the window off fullscreen, and that causing the window handle create
  to fail.

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