Fix T48470: Bendy Bones: Custom Handle References not being cleared when bone deleted

In addition to the original bug report, I've gone through cleaning up a range of
related bugs which only became clear when hunting around the code...

* Custom Handle References weren't getting cleared when the bones they used got
  deleted.  But, neither was the custom bone shape location/transform reference.

* Various places where posebone settings are copied around were also missing code
  to handle the new Bendy Bone properties.

  (WHY DO WE HAVE SO MANY VARIATIONS OF COPYING POSE DATA!?!?)

* If duplicating a Bendy Bone with custom references, and the custom references
  are also selected/duplicated, the new Bendy Bones will use the corresponding
  duplicated bones

1 files changed, 6 insertions, 0 deletions

diff --git a/source/blender/editors/armature/armature_add.c b/source/blender/editors/armature/armature_add.c
index 847b45d612c..559d93c7eb1 100644
--- a/source/blender/editors/armature/armature_add.c
+++ b/source/blender/editors/armature/armature_add.c
@@ -348,6 +348,12 @@ void postEditBoneDuplicate(struct ListBase *editbones, Object *ob)
 					if (pchan_src->custom_tx) {
 						pchan_dst->custom_tx = pchan_duplicate_map(ob->pose, name_map, pchan_src->custom_tx);
 					}
+					if (pchan_src->bbone_prev) {
+						pchan_dst->bbone_prev = pchan_duplicate_map(ob->pose, name_map, pchan_src->bbone_prev);
+					}
+					if (pchan_src->bbone_next) {
+						pchan_dst->bbone_next = pchan_duplicate_map(ob->pose, name_map, pchan_src->bbone_next);
+					}
 				}
 			}
 		}