[1.0.0.341] Rivers not displayed in 3D view on custom maps after calling GenerateFloodplains()

[Gedemon]

There have been a few reports of a new bug that seems to have been introduced by the last civ6 patch when using YnAMP:

• Rivers are not displayed in 3D view on some maps (Nile on the Play Europe Again map for example,) after calling TerrainBuilder.GenerateFloodplains()

Something has been changed between 1.0.0.318 and 1.0.0.341 in that function and seems to mess river placement, but I can't fix it on the mod side because it's not exposed to modding (as every other rivers function AFAIK)

Not calling TerrainBuilder.GenerateFloodplains() prevent the issue and the rivers are correctly displayed as before (but then you can't set a random placement of floodplains, which was working perfectly fine before)