Error "No such parameter 'den_palette'" being thrown during build checks randomly

[furran]

Describe the bug

I've noticed that recently ( the last few days ) new pull requests have been failing checks because of the following error:

(all_mods)=> Backtrace emission took 2 seconds.
(all_mods)=> (continued from above) ERROR : src/mapgendata.h:244 [Result mapgendata::get_arg(const std::string &) const [Result = string_id<mapgen_palette>]] No such parameter "den_palette"
(all_mods)=> [ Previous repeated 61 times ]
(all_mods)=> 11:37:19.079 ERROR : src/mapgendata.h:244 [Result mapgendata::get_arg(const std::string &) const [Result = string_id<mapgen_palette>]] No such parameter "den_palette"

This is not a failed test, it's a test throwing an error.

The culprit seems to be the trail.json file introduced in #67470, as it is the only place I could find related to mapgen that had "den_palette" and it matches the timeline I felt it started happening.

I don't really know how to fix this properly.

Attach save file

N/A

Steps to reproduce

It is seemingly random. But chances are if you created pull requests recently, you have seen this error.

Expected behavior

The mapgen tests do not throw errors

Screenshots

No response

Versions and configuration

N/A

Additional context

Some PRs with this error in their checks for anyone who wants to check: #70163 #70184 #70149 #70120

[physics-enthusiast]

Seeing an error about den_palette thrown in gameplay occasionally as well, although I don't remember the specific message and can't reproduce whatever is causing it.

[GoLoT]

I saw this too while loading a new overmap tile in a new world (created 2 days ago on latest experimental at the time). The error message was the same as in the tests and it showed up multiple times per overmap tile. I only had it happen twice so far but I didn't continue exploring.

[Maleclypse]

Fixed by #70248