Fix #30720: Creating Navmesh crashes blender

In fact there were several issues fixed (all of them regressions since bmesh merge):

- Creating navmesh crashed because creating new faces for mesh was trying to set
  default values for all customdata layers in this face. This requires memory
  pool created for this datablock.
  Usually this pool is creating on creating datablock if there're some elements
  to be stored in this block. In cases of regular primitive creating it wasn't
  an issue because they doesn't create customdata layers, they only creates
  geometry.
  Navigation mesh creates geometry and customdata layers (CD_RECAST layer)
  which used to confuse a bit custom data functions. Solved by ensuring there's
  memory pool created for polygons datablock after adding new custom data layer.
  Most probably it's better to be resolved on CD level (like smarter track on
  changed amount of stored data and so) but prefer not to make such global changes
  so close to the release.
- Toggling edit mode lead to loosing recast datalayer. Solved by adding recast
  layer to bmesh mask so it'll be copied to/from edit mesh.
- Some part of code assumed raycast layer is in face datablock, some that it's in
  polygon datablock. Made it to be in polygons datablock.
  Kind of temporary solution to make navmesh working, probably it'll fail if one
  will want to edit navmesh by hand after it was generated.
  Proper way would be to ensure the whole navmesh things are using ngons.

1 files changed, 1 insertions, 0 deletions

diff --git a/source/blender/editors/mesh/mesh_navmesh.c b/source/blender/editors/mesh/mesh_navmesh.c
index f1b0a82b654..7d78a527b06 100644
--- a/source/blender/editors/mesh/mesh_navmesh.c
+++ b/source/blender/editors/mesh/mesh_navmesh.c
@@ -345,6 +345,7 @@ static Object *createRepresentation(bContext *C, struct recast_polyMesh *pmesh,
 
 	/* create custom data layer to save polygon idx */
 	CustomData_add_layer_named(&em->bm->pdata, CD_RECAST, CD_CALLOC, NULL, 0, "createRepresentation recastData");
+	CustomData_bmesh_init_pool(&em->bm->pdata, 0, BM_FACE);
 	
 	/* create verts and faces for detailed mesh */
 	meshes = recast_polyMeshDetailGetMeshes(dmesh, &nmeshes);