OpenTreeMap/OTM2 — pull request #1621 by steventlamb (2014-09-18 20:51:03+00:00)
Title: Cleanup UI properly after error

I observed that after a failure, the UI did not clean itself up
properly. Subsequent exports worked, but would continue to display the
earlier failure message.

I reworked the displayManager to be a little simpler as well.