step cannot be zero

[maartenvd]

I think empty blocks still cause issues, because this fails somewhere deep in strided :

t = TensorMap(rand,ComplexF64,ProductSpace(U₁Space(0=>12, 1=>0, -1=>12, -2=>12)) ← (U₁Space(0=>1)' ⊗ U₁Space(0=>12, 1=>12, -1=>12)))
mul!(similar(t,ComplexF64),t,1/norm(t))

[Jutho]

Yes the problem is actually with the U₁Space constructor; it should just ignore zero-dimensional sectors and remove them.