Null ref exception on CellSet.Update

[Zematus]

Running Worlds 0.3.4 alpha 2 (WindowsPlayer Debug)...
Trying to generate world with seed: 1040784865, Altitude Scale: 0,75, Sea Level Offset: 0, River Strength: 0,5, Avg. Temperature: 13,7, Avg. Rainfall: 990
Active Mods: Mods\Base
[Date: Year 0, Day 0] - Finished generating world with seed: 1040784865
[Date: Year 0, Day 0] - Active Mods: Mods\Base
[Date: Year 0, Day 0] - Player went back to mode selection dialog.
[Date: Year 0, Day 0] - Game entered map editor mode.
[Date: Year 0, Day 0] - NeedsDrainageRegeneration set to true
[Date: Year 0, Day 0] - NeedsDrainageRegeneration set to true
[Date: Year 0, Day 0] - Trying to regenerate world with seed: 1040784865, Altitude Scale: 0,75, Sea Level Offset: 0, River Strength: 0,5, Avg. Temperature: 13,7, Avg. Rainfall: 990
[Date: Year 0, Day 0] - Finished regenerating world with seed: 1040784865
[Date: Year 0, Day 0] - Player went back to mode selection dialog.
[Date: Year 0, Day 0] - Game entered map editor mode.
[Date: Year 0, Day 0] - Player went back to mode selection dialog.
[Date: Year 0, Day 0] - Game entered history simulator mode.
[Date: Year 0, Day 0] - Player set starting speed to 7...
[Date: Year 0, Day 0] - Player chose to select cell for population placement of 5019...
[Date: Year 0, Day 0] - Adding population group at [58,101] with population: 5019
[Date: Year 534360, Day 359] - Removing polity prominence of faction that had core in group 0000000000051379367:0173399394292868736, removing faction 0000000000195041737:0173399394292868736 - polity: 0000000000195041737:0173399394292868736 - Date:195041759
[Date: Year 891551, Day 178] - NullReferenceException: Object reference not set to an instance of an object
CellSet.Update () (at C:/Users/jb_ta/Documents/GitHub/Worlds/Assets/Scripts/WorldEngine/Terrain/CellSet.cs:94)
CellSet+d__18.MoveNext () (at C:/Users/jb_ta/Documents/GitHub/Worlds/Assets/Scripts/WorldEngine/Terrain/CellSet.cs:281)
CellSubRegionSetBuilder+d__7.MoveNext () (at C:/Users/jb_ta/Documents/GitHub/Worlds/Assets/Scripts/WorldEngine/Regions/CellSubRegionSetBuilder.cs:37)
System.Collections.Generic.List1[T].InsertRange (System.Int32 index, System.Collections.Generic.IEnumerable1[T] collection) (at <4756199cf52a4f14b33cdcc5659f782e>:0)
System.Collections.Generic.List1[T].AddRange (System.Collections.Generic.IEnumerable1[T] collection) (at <4756199cf52a4f14b33cdcc5659f782e>:0)
CellSubRegionSetBuilder.GenerateRegionFromCellSet (TerrainCell startCell, CellSet cellSet, Language language) (at C:/Users/jb_ta/Documents/GitHub/Worlds/Assets/Scripts/WorldEngine/Regions/CellSubRegionSetBuilder.cs:127)
BiomeCellRegionBuilder.TryGenerateRegion (TerrainCell startCell, Language language, System.Collections.Generic.HashSet`1[T] cellsToIgnore) (at C:/Users/jb_ta/Documents/GitHub/Worlds/Assets/Scripts/WorldEngine/Regions/BiomeCellRegionBuilder.cs:318)
Region.TryGenerateRegion (TerrainCell startCell, Language establishmentLanguage) (at C:/Users/jb_ta/Documents/GitHub/Worlds/Assets/Scripts/WorldEngine/Regions/Region.cs:166)
TerrainCell.GetRegion (Language initLanguage) (at C:/Users/jb_ta/Documents/GitHub/Worlds/Assets/Scripts/WorldEngine/Terrain/TerrainCell.cs:583)
Polity..ctor (System.String type, CellGroup coreGroup, System.Int64 idOffset) (at C:/Users/jb_ta/Documents/GitHub/Worlds/Assets/Scripts/WorldEngine/Polities/Polity.cs:319)
Tribe..ctor (CellGroup coreGroup) (at C:/Users/jb_ta/Documents/GitHub/Worlds/Assets/Scripts/WorldEngine/Polities/Tribe.cs:35)
TribeFormationEvent.Trigger () (at C:/Users/jb_ta/Documents/GitHub/Worlds/Assets/Scripts/WorldEngine/Events/TribeFormationEvent.cs:115)
World.EvaluateEventsToHappen () (at C:/Users/jb_ta/Documents/GitHub/Worlds/Assets/Scripts/WorldEngine/World.cs:1492)
GuiManagerScript.Update () (at C:/Users/jb_ta/Documents/GitHub/Worlds/Assets/Scripts/2D/GuiManagerScript.cs:618)

[Zematus]

debug_18_04_2021_12_37_31.log

[Zematus]

debug_21_05_2021_11_30_35.log