map editor refuses to load some maps

[Hamplmann]

Describe the bug
The in-game map editor does not load maps that come pre-packaged with the game
maps that are located in campaign-subfolders are not affected by this behaviour

To Reproduce
Steps to reproduce the behavior:

1. Open the map editor
2. it shows the default, plains-only map template
3. click
   Menu -> load map
   and select a map (that is included in the vanilla game) to load
4. the currently edited map stays as the default, plains-only map template

Expected behavior
the currently edited map should show the map that was selected to be loaded

Screenshots
none

Desktop (please complete the following information):

• OS: Windows 11
• Active Mods: none
• Game Version: Beta 38_5

Additional context
none