Invalid big Tree behavior when scrolling is enabled

[KoBeWi]

Tested versions

4.5 dev4

System information

W10

Issue description

While testing #105967 I noticed there is opposite bug. When you enable scrolling, Tree's minimum size is not determined correctly.

With scrolling disabled:

(scrollbars are visible, this is #105967)

With scrolling enabled:

The tree for whatever reason becomes super big and no longer fits the screen. It's like enabling scrolling causes the contents no longer properly ignored when calculating minimum size.

Steps to reproduce

1. Run the MRP.

Minimal reproduction project (MRP)

tree_mre.zip