vertical scrollbar not updated when QTreeView resized

[pobere]

hello,

I have the following:
A vertical QSplitter with: an edit control and a QFrame.
The QFrame has a vertical layout: toolbar and a QTreeView

The problem is the following: when I change the splitter position,
the vertical scrollbar of the QTreeView is not updated.
For example, we have in QTreeView 10 items and we can see all af them; after moving
the splitter to make the QTreeView smaller (we can see now only 5 items) a vertical scroolbar should
appear, but it doesn't. After clicking different items in the tree, the vertical scroll bar is updated and correctly displayed.

Capture1.PNG

Capture2.PNG

What could be the problem?

Many thanks!!!