Closing (cancelling) commit selection window while merging minimizes the Merge dialog

The Merge dialog offers to spawn a window to select which commit to merge. But if one does not find the commit there and decides to simply close the selection window (with either Cancel or the "X" at top right), the Merge dialog is strangely hidden (the window focused will be the Explorer, not the Merge window).

To reproduce:

1. Invoke the Merge dialog (right-click a checkout and select TortoiseGit->Merge...)
2. Click the Commit radio box
3. Click the ellipsis button at the right.
4. Click the "Cancel" button

Expectation: The Merge window is at the foreground

Reality: Depending on the exact sequence, the Merge window may be hidden. If another window is selected between 1 and 3, it looks like the Merge window remains at the foreground as expected.

This happens with TortoiseGit 2.9.0.0 on Windows 8.