context buttons don't appear for coffins.

[kypvalanx]

when i start a new game with this mod the buttons don't appear when i select a coffin. i think the culprit might be this invalid cast exception:

Vampire settings applied.
Unloading 5 Unused Serialized files (Serialized files now loaded: 1)

Unloading 51 unused Assets to reduce memory usage. Loaded Objects now: 11547.
Total: 100.085000 ms (FindLiveObjects: 0.822800 ms CreateObjectMapping: 0.588200 ms MarkObjects: 98.617600 ms  DeleteObjects: 0.055900 ms)

Unloading 3 Unused Serialized files (Serialized files now loaded: 1)
UnloadTime: 0.190100 ms

Unloading 13 unused Assets to reduce memory usage. Loaded Objects now: 11862.
Total: 101.725100 ms (FindLiveObjects: 0.553900 ms CreateObjectMapping: 0.655200 ms MarkObjects: 100.464000 ms  DeleteObjects: 0.051700 ms)

Initializing new game with mods:
  - brrainz.harmony
  - Ludeon.RimWorld
  - Ludeon.RimWorld.Royalty
  - UnlimitedHugs.HugsLib
  - jecrell.jecstools
  - fluffy.modmanager
  - rimofmadness.vampires
Unloading 0 Unused Serialized files (Serialized files now loaded: 1)

Unloading 0 unused Assets to reduce memory usage. Loaded Objects now: 17260.
Total: 142.491600 ms (FindLiveObjects: 0.786400 ms CreateObjectMapping: 1.163400 ms MarkObjects: 140.502300 ms  DeleteObjects: 0.039100 ms)

System.InvalidCastException: Specified cast is not valid.
  at RimWorld.CompAssignableToPawn_Bed.ShouldShowAssignmentGizmo () [0x00000] in <0ee2c524c4be441e9b7f8bfcb20aca6f>:0 
  at RimWorld.CompAssignableToPawn+<CompGetGizmosExtra>d__27.MoveNext () [0x0001e] in <0ee2c524c4be441e9b7f8bfcb20aca6f>:0 
  at Vampire.Building_Coffin+<GetGizmos>d__8.MoveNext () [0x00119] in <be885b18395548cdb5c0a44582d149f7>:0 
  at System.Collections.Generic.List`1[T].InsertRange (System.Int32 index, System.Collections.Generic.IEnumerable`1[T] collection) [0x000db] in <567df3e0919241ba98db88bec4c6696f>:0 
  at System.Collections.Generic.List`1[T].AddRange (System.Collections.Generic.IEnumerable`1[T] collection) [0x00000] in <567df3e0919241ba98db88bec4c6696f>:0 
  at RimWorld.InspectGizmoGrid.DrawInspectGizmoGridFor (System.Collections.Generic.IEnumerable`1[T] selectedObjects, Verse.Gizmo& mouseoverGizmo) [0x00045] in <0ee2c524c4be441e9b7f8bfcb20aca6f>:0 
 
(Filename: C:\buildslave\unity\build\Runtime/Export/Debug/Debug.bindings.h Line: 35)

i don't know enough about rimworld modding to figure out more.