Revert "Fix bug: B65-ZK-1568"
- This reverts commit 23efa4cff5ca61d1ff597c2e23fd6daca44c59de.
- Spec note: setting mode to a non-modal mode will always make the window visible
  <window visible="false" mode="overlapped" /> should be considered misuse and must be avoided.
Merge branch 'B65-ZK-1568' of git://github.com/leeyt/zk