
I do have a Red desert in the north. The savegame was started in 0.15.x .
Edit: I did revert to v0.15.10 to make double sure it is a 15.11 issue. And as expected the savegame loaded fine.
when I looked through the files I noticed that in prototypes/decorative/decoratives.lua all entries for the
"red-desert-decal" optimised-decoratives were removed.
So I put it back in decoratives.lua and the error message disappears.
For now I will be playing 0.15.11 with the 15.10 desert-decals-entries until told otherwise

Can I safely ignore this and overwrite my savegame or will I be running the risk of corrupting it?