System Information
Operating system and graphics card
Fedora, Intel Graphics
Blender Version
latest blender2.8 branch from git
Short description of error
the python below should add points to the new vertex group, but it fails.
Exact steps for others to reproduce the error
v = ob.vertex_groups.new(name="mygroup")
v.add( [1,2,3], weight=1.0, type="ADD")