HL2:DM (x64) doesn't load maps in multiplayer

[ThePixelMoon]

Describe the bug
When a map is loaded in multiplayer (maxplayers 2+), the game gives an error about Steam needing to be ran to connect to multiplayer servers.

To Reproduce
Steps to reproduce the behavior:

1. Set maxplayers 2
2. Load a map
3. See error

Expected behavior
The map running fine

Screenshots

Desktop (please complete the following information):

• OS: Windows 10 22H2
• Application version: 1.3.2.5133

Additional context
This possibly happens due to the NO_STEAM definition on. A commit on another Source-related repo (nillerusr/source-engine@f7233c8) fixes it. (?)