617 Tree visibility per tab broken

[Scott_Y]

1. Enable "Tree visibility per tab" (Settings > Tree > General tab).
2. Open a tree in a tab.
3. Switch to another tab and back to the first tab.
4. The tree is no longer displayed in the first tab.

This applies to at least 616 and 617; I didn't test earlier versions. Win7 x64.

[alf5000]

confirmed

[Marek]

Fixed for the release 619.