Errors in `TreeSA()` - Githubissues

Here is a MWE.
julia> using OMEinsum, OMEinsumContractionOrders

julia> ec = EinCode([[1],[2],[2],[1]], Int[])
1, 2, 2, 1 -> 

julia> ts = [rand(2) for _ = 1:4];

julia> optimize_code(ec, uniformsize(ec, 2), TreeSA())
ERROR: MethodError: Cannot `convert` an object of type 
  NestedEinsum{OMEinsum.DynamicEinCode{Int64}} to an object of type 
  NestedEinsum{OMEinsum.DynamicEinCode{Union{}}}
Closest candidates are:
  convert(::Type{T}, ::T) where T at essentials.jl:205
Stacktrace:
  [1] setindex!(A::Vector{NestedEinsum{OMEinsum.DynamicEinCode{Union{}}}}, x::NestedEinsum{OMEinsum.DynamicEinCode{Int64}}, i1::Int64)
    @ Base ./array.jl:843
  [2] _unsafe_copyto!(dest::Vector{NestedEinsum{OMEinsum.DynamicEinCode{Union{}}}}, doffs::Int64, src::Vector{NestedEinsum{OMEinsum.DynamicEinCode{Int64}}}, soffs::Int64, n::Int64)
    @ Base ./array.jl:235
  [3] unsafe_copyto!
    @ ./array.jl:289 [inlined]
  [4] _copyto_impl!
    @ ./array.jl:313 [inlined]
  [5] copyto!
    @ ./array.jl:299 [inlined]
  [6] copyto!
    @ ./array.jl:325 [inlined]
  [7] copyto_axcheck!
    @ ./abstractarray.jl:1056 [inlined]
  [8] Vector{NestedEinsum{OMEinsum.DynamicEinCode{Union{}}}}(x::Vector{NestedEinsum{OMEinsum.DynamicEinCode{Int64}}})
    @ Base ./array.jl:540
  [9] convert
    @ ./array.jl:532 [inlined]
 [10] NestedEinsum(args::Tuple{NestedEinsum{OMEinsum.DynamicEinCode{Int64}}, NestedEinsum{OMEinsum.DynamicEinCode{Int64}}}, eins::OMEinsum.DynamicEinCode{Union{}})
    @ OMEinsum ~/.julia/packages/OMEinsum/MTnLO/src/einsequence.jl:166
 [11] _nestedeinsum(tree::OMEinsumContractionOrders.ExprTree, lbs::Dict{Int64, Int64})
    @ OMEinsumContractionOrders ~/.julia/packages/OMEinsumContractionOrders/jLE2Q/src/treesa.jl:312
 [12] NestedEinsum
    @ ~/.julia/packages/OMEinsumContractionOrders/jLE2Q/src/treesa.jl:308 [inlined]
 [13] optimize_tree(code::OMEinsum.DynamicEinCode{Int64}, size_dict::Dict{Int64, Int64}; sc_target::Int64, βs::StepRangeLen{Float64, Base.TwicePrecision{Float64}, Base.TwicePrecision{Float64}}, ntrials::Int64, niters::Int64, sc_weight::Float64, rw_weight::Float64, initializer::Symbol, greedy_method::MinSpaceOut, greedy_nrepeat::Int64)
    @ OMEinsumContractionOrders ~/.julia/packages/OMEinsumContractionOrders/jLE2Q/src/treesa.jl:96
 [14] _optimize_code
    @ ~/.julia/packages/OMEinsumContractionOrders/jLE2Q/src/interfaces.jl:43 [inlined]
 [15] optimize_code
    @ ~/.julia/packages/OMEinsumContractionOrders/jLE2Q/src/interfaces.jl:22 [inlined]
 [16] optimize_code(code::OMEinsum.DynamicEinCode{Int64}, size_dict::Dict{Int64, Int64}, optimizer::TreeSA{Int64, StepRangeLen{Float64, Base.TwicePrecision{Float64}, Base.TwicePrecision{Float64}}, GreedyMethod{MinSpaceOut}})
    @ OMEinsumContractionOrders ~/.julia/packages/OMEinsumContractionOrders/jLE2Q/src/interfaces.jl:21
 [17] top-level scope
    @ REPL[62]:1
TensorBFS / OMEinsumContractionOrders.jl

Errors in `TreeSA()` #18
