Fix incorrect mesh selection duplication in internal utility function

`BKE_mesh_new_nomain_from_template_ex()` would duplicate the mesh selection
storage of the destination mesh to the destination mesh. Since that mesh was
default initialized at this point, the selection was `NULL`, so the duplication
call is essentially a no-op.

Mistake in 7efc75c709.

Differential Revision: https://developer.blender.org/D10009

Reviewed by: Sybren Stüvel

source/blender/blenkernel/intern/mesh.c

@@ -941,7 +941,7 @@ Mesh *BKE_mesh_new_nomain_from_template_ex(const Mesh *me_src,
 
   Mesh *me_dst = BKE_id_new_nomain(ID_ME, NULL);
 
-  me_dst->mselect = MEM_dupallocN(me_dst->mselect);
+  me_dst->mselect = MEM_dupallocN(me_src->mselect);
 
   me_dst->totvert = verts_len;
   me_dst->totedge = edges_len;