[Win32] CTabFolder header is missing

[HeikoKlare]

Describe the bug
The header of a CTabFolder may not be rendered.
This is a regression from #2336

To Reproduce
Start the CustomControlExample and go to the CTabFolder tab or open the global search (CTRL+H) in an Eclipse application (see screenshots below).

Expected behavior
CTabHolder header should be rendered properly.

Screenshots

Environment:

1. Select the platform(s) on which the behavior is seen:

• • All OS
• • Windows
• • Linux
• • macOS

2. Additional OS info (e.g. OS version, Linux Desktop, etc)
   WIndows-only

3. JRE/JDK version
   ireelevant

Version since
Since I20250723-1800 (as regression was introduced in day before, see above).