fix 0.4 issue with the callback addition
fix 0.4 issue with the callback addition

JuliaPackageMirrors/Optim.jl,pkofod/Optim.jl,KristofferC/Optim.jl,pkofod/Optim.jl,yuyichao/Optim.jl,matthieugomez/Optim.jl,JuliaPackageMirrors/Optim.jl,KristofferC/Optim.jl,yuyichao/Optim.jl,matthieugomez/Optim.jl