Game crash on schematic save when mod WorldEdit is not trusted

[pauldpickell]

Describe the bug
When the WorldEdit mod is not added to the list of trusted mods for the client, then the game crashes when attempting to save a schematic.

To Reproduce
Steps to reproduce the behavior:

1. Ensure WorldEdit is not listed in trusted mods. This is the default for a new client.
2. Run chat command \realm schematic save [current realmID]
3. Observe server crash and debug output below.

2023-06-11 14:21:59: ACTION[Server]: Prof_Pickell uses mc_teacher:controller, pointing at [node under=-4120,-29997,-29959 above=-4120,-29996,-29959]
2023-06-11 14:22:27: [Server]: nil
2023-06-11 14:22:27: ACTION[Main]: Server: Shutting down
2023-06-11 14:22:27: ACTION[Server]: Prof_Pickell leaves game. List of players:
2023-06-11 14:22:28: ERROR[Main]: ServerError: AsyncErr: Lua: Mod security: Blocked attempted write to /home/ubuntu/minetest/bin/../worlds/UBCWorld\realmSchematics\

[pauldpickell]

This is possibly related to how map chunks are loaded via the realm management system.