Fix T61353: Crash converting a curve to a mesh

This was caused by curves pointing to each other
creating a cyclic dependency.

While the dependency graph detects this, generating a mesh for render
recursively generates data which cashes in this case.

Add in a check to detect cyclic links.

Note, this bug exists in 2.7x too - but only crashes on render
since 2.7x didn't use 'for_render' when converting data.

1 files changed, 1 insertions, 1 deletions

diff --git a/source/blender/editors/object/object_add.c b/source/blender/editors/object/object_add.c
index 2931fb89d7e..a6360ac2e38 100644
--- a/source/blender/editors/object/object_add.c
+++ b/source/blender/editors/object/object_add.c
@@ -1771,7 +1771,7 @@ static void convert_ensure_curve_cache(Depsgraph *depsgraph, Scene *scene, Objec
 		if (ELEM(ob->type, OB_SURF, OB_CURVE, OB_FONT)) {
 			/* We need 'for render' ON here, to enable computing bevel dipslist if needed.
 			 * Also makes sense anyway, we would not want e.g. to loose hidden parts etc. */
-			BKE_displist_make_curveTypes(depsgraph, scene, ob, true, false);
+			BKE_displist_make_curveTypes(depsgraph, scene, ob, true, false, NULL);
 		}
 		else if (ob->type == OB_MBALL) {
 			BKE_displist_make_mball(depsgraph, scene, ob);