Scrolbars are not correctly themed under certain cirumstances

[joachimmarder]

Repro steps

• Open project "Advanced.dproj"
• In project options set a VCL style, e.g. "Amakrits", under "Appearance"
• Run the project
• Go to the 4th tab "Hide and show nodes"
• In the control on the top left expand a node
• The now appearing scrollbar is not styled (see attached screenshot)

Thanks @Kidi1961 for reporting the issue and supplying a patch.

[joachimmarder]

Proposed patch:
VirtualTrees.pas.patch.zip