When using NoMachine on a Windows 11 server with duplicated displays, the screen blanking feature does not work correctly. The second monitor remains visible instead of being blanked.

Steps to reproduce:
1. Enable the configuration key: EnableScreenBlanking 1 in server.cfg file
2. On Windows 11 server go to: settings -> system -> display -> set 'duplicate these displays'
3. Connect to Windows server: the issue is that the second monitor remains visible and is not blanked.

As a workaround, set the monitors to 'extend these displays': blanking will be set correctly.