How to prevent output switching from monitor (VGA) to TV (DVI)?

My OS now is Kubutnu 18.04 64 bit. I use proprietary nvidia drivers with xorg server. The card is GT 730

Driver version: 390.116
Server Version Number: 11.0
Server Vendor String: The X.Org Foundation
Server Vendor Version: 1.19.6 (11906000)
NV-CONTROL Version: 1.29
Screens: 1

Monitor is on VGA port, TV is turned off and on DVI port. The issue i have is that some native applications (games) such as for example World of Padman or Battle for Wesnoth switch automatically to TV output (even when it is off). This happens despite having only monitor enabled, TV off and displays in “System settings” show only the monitor being enabled. The output still switches to TV. How do i prevent displays from switching? I want only monitor to be working. Also at boot the TV output is used, even if TV is off.